The aging report has been sitting in your billing inbox since Tuesday. The 90+ day column is longer than it should be, your billing coordinator is stretched across three other tasks, and knowing how to recover aged dental AR systematically, bucket by bucket is the difference between writing thousands of dollars off and actually getting paid.

This guide gives you a concrete protocol for every aging bucket: what to do, in what order, and how to decide when it's no longer worth pursuing an account. It covers the 0–30, 31–60, 61–90, and 90+ day buckets separately, explains why insurance AR and patient AR require entirely different recovery strategies, and provides a clear write-off decision framework so your team stops guessing and starts acting.

The goal is not to chase every aged balance it's to allocate effort where recovery is still probable and protect your team's time from accounts that have passed the point of return. Understanding how to recover aged dental AR by aging bucket is the foundation of a revenue cycle that actually protects your practice's cash flow.

How to recover aged dental AR: Apply a separate recovery protocol for each aging bucket clean claim submission and prompt patient statements at 0–30 days (95%+ recovery rate); denial appeals and SMS billing reminders at 31–60 days (70–85%); direct patient calls and structured payment plans at 61–90 days (50–70%); and triage between collection agency referral, settlement offer, or write-off at 90+ days (15–25%). Always separate insurance AR from patient AR at every stage.

Quick Reference Dental AR Recovery by Aging Bucket

Recovery rates drop sharply after 60 days. The 61–90 day window is your last reliable chance at full collection after 90 days, triage first, pursue second.

Key Takeaways

• Dental practices typically recover only 15–25% of AR that reaches 90+ days, according to dental AR benchmark data consistent action at 31–60 days is the most effective strategy for protecting revenue.
• Best-performing practices keep dental AR over 90 days below 3% of total AR practices with AR consistently above this threshold face significant revenue leakage.

The root causes behind these numbers are consistent across practice types:

• Insurance AR and patient AR require completely different playbooks treating them the same workflow is one of the most common billing mistakes in dental practices.
• Your dental net collection rate should be 98%+ if it's consistently below that, aged AR is likely the primary drag on your practice financials.
• A clear, consistently applied write-off and collection referral policy recovers more than ad-hoc pursuit of every aging account.

How We Built This Protocol

The recovery rates and action triggers in this guide draw on published dental AR benchmarks from IC System, Pearly.co, and DentaLBillingAssist, plus review of billing workflows across solo practices, group practices, and multi-location DSOs. Our analysis of dental AR patterns identified three consistent predictors of aged AR: missed insurance appeal deadlines, delayed patient statements, and undifferentiated billing queues that mix insurance and patient follow-up in the same workflow.

The protocols for each aging bucket are sequenced to match the actual recovery curve not arbitrary 30-day intervals. Based on our evaluation, the 31–60 day window is the single highest-leverage stage in dental AR recovery: it has the best combination of recovery probability (70–85%) and sufficient time to act before insurance appeal windows close. Most practices underinvest here and overwork the 90+ bucket, where recovery rates fall to 15–25%.

Before You Start: What You'll Need

Before working your AR aging report, confirm the following are in place:

• PMS access and AR aging report capability You need to run an aging report filtered separately by payer and by patient. Know how to generate this in your practice management software (OpenDental, EagleSoft, Denticon, CareStack, or Curve Dental). A combined report doesn't give you enough resolution to apply different strategies.
• Staff assignment by bucket - One person should own each bucket's follow-up for a given work period. Diffused ownership means nothing gets worked consistently.
• Insurance plan appeal deadlines on file - Most payers allow appeals within 60–180 days from the date of claim processing. If you don't know each payer's deadline, pull them from your provider agreements before you begin.

These policy requirements must also be defined before you begin working aged accounts:

• Collection agency contact on file - If you don't have a vetted collection partner, identify one before balances reach 120+ days.
• Write-off authority and dollar thresholds defined - Establish in advance who can approve a write-off and at what balance amounts. Ad-hoc write-off decisions create inconsistency and audit risk.
• Benchmark context - Review your practice's claim rejection rate benchmarks before diving into insurance AR. If your rejection rate is high with a specific payer, that's a systemic billing issue not just an aging problem.

What Aged Dental AR Actually Costs Your Practice

Aged dental AR (accounts receivable) refers to outstanding patient and insurance balances that remain unpaid beyond their expected collection window, grouped into aging buckets: 0–30, 31–60, 61–90, and 90+ days. Each bucket has a distinct recovery rate and requires a different protocol which is why a single undifferentiated follow-up process consistently underperforms.

The real cost of aged dental AR is not just the uncollected balance it's the compounding loss of recovery probability over time. Recovery rates fall sharply after the 90-day mark, and after six months, full recovery without external collection help is statistically near zero.

Most practices allow significant balances to sit unworked in the 90+ bucket without a structured protocol. Best-performing dental practices hold AR over 90 days under 3% of total AR, according to dental AR benchmark data.

For DSOs, the stakes extend beyond cash flow. A $100,000 bad debt write-off reduces EBITDA dollar-for-dollar and at a 5x valuation multiple, that single write-off reduces enterprise value by $500,000. For multi-location groups preparing for acquisition or investment, aged AR on the balance sheet is a material liability.

The solution is not to work harder across all aged accounts. It is to apply a protocol matched to the realistic recovery probability for each aging bucket and stop investing staff time in accounts where the math no longer works.

Three factors consistently predict aged AR across practice types: missed insurance appeal deadlines, delayed patient statements, and billing queues that mix insurance and patient follow-up in one undifferentiated workflow. This guide addresses all three.

Step 1 Audit Your AR Aging Report

Audit your aging report to separate insurance from patient balances, identify expired appeal windows, and rank remaining accounts by recovery probability before making a single outreach attempt.

Run this audit at the start of every weekly work session:

1. Split insurance AR from patient AR - Many PMS systems combine these in the default aging view. Create two working lists before doing anything else.
2. Sort each bucket by balance, descending - Work the highest balances first.
3. Flag expired insurance appeal windows - For claims in the 61–90 or 90+ bucket, verify whether the payer's appeal deadline is still open. Expired windows cannot be reopened.
4. Check for duplicate or in-transit payments - A 90+ day balance may already have payment in the clearinghouse pipeline. Check payer portals first.
5. Identify zero-activity accounts - Balances with no payment, no denial response, and no patient contact at 60+ days need immediate escalation, not routine follow-up.
6. Note patient communication history - A patient with multiple non-responses is categorically different from one who hasn't received a statement. Check your PMS contact log first.

Do this weekly not monthly. By Day 60, many insurance appeal windows are already closing and your recovery options have narrowed significantly.

Aging Bucket Recovery Summary

Before beginning bucket-by-bucket recovery, use this table to set expectations and allocate staff time appropriately:

Recovery rate estimates based on industry benchmark data from IC System and Pearly.co.

Step 2 How to Recover 0–30 Day AR

Recovering 0–30 day dental AR is primarily a prevention play clean claim submission, eligibility verification at intake, and prompt patient statements that stop problems before they age into the next bucket.

Accounts in this range have not yet become a problem. Your job is to ensure they don't.

For Insurance Balances

• Verify every submitted claim was received and accepted by the clearinghouse. Check acknowledgment reports within 48 hours of submission a rejected claim that sits for two weeks has already lost time in the appeal window.
• Confirm patient eligibility and coverage was verified before treatment. Eligibility mismatches are the leading driver of preventable denials. If verification was skipped, correct the claim record now.

If claims are received but delayed or denied, check the specifics:

• For any claim showing "pending" at Day 14, check the payer portal directly or call the provider line to confirm processing status. A 14-day check is standard practice for insurers that typically turn around clean claims within that window.
• If a claim was denied in this range, pull the denial reason immediately. The most common causes include missing CDT codes, missing attachments (X-rays, periodontal charting, clinical narratives), frequency limitations, and credentialing mismatches between the treating dentist and the billed provider.

For Patient Balances

• Send the first patient statement promptly after the insurance EOB posts not after 30 days. Delayed statements are the most common reason patient balances begin to age.
• Include an itemized breakdown, the insurance payment applied, and the remaining patient responsibility clearly labeled. Patients who don't understand their balance defer payment.
• Add a digital payment link or QR code to paper statements. Practices that make payment accessible without a phone call or office visit see faster first-payment response rates.

The target in the 0–30 bucket is a 95%+ resolution rate. Any balance that exits this window unresolved needs the 31–60 escalation protocols applied immediately at Day 31 not at your next monthly billing review.

Step 3 How to Recover 31–60 Day AR

Recovering 31–60 day dental AR requires proactive denial appeals and structured patient outreach before insurance deadlines narrow and patient payment momentum stalls.

Accounts in the 31–60 day bucket are at risk but still highly recoverable 70–85% with consistent follow-up. This is where reactive billing practices lose money that proactive ones collect without significant effort.

For Insurance Balances

Pull all denials received in this bucket and categorize by denial reason before doing anything else. Common denial categories:

• Missing or incorrect CDT codes
• Missing attachments (X-rays, periodontal charting, operative notes)
• Frequency limitations exceeded
• Credentialing mismatch between treating provider and billed provider
• Duplicate claim submission
• Patient eligibility or coverage not active on date of service

File appeals immediately after categorizing. Most payers require appeals within 60–180 days from the date of processing, per Capline Dental Services. If a claim was denied at Day 20 and you don't appeal until Day 55, some payers leave you fewer than 30 days to respond. Always address the specific denial reason with supporting documentation re-filing the same claim without addressing the denial reason produces the same denial.

Track your denial rate by payer. A payer generating a 20%+ denial rate on your claims needs a billing workflow review not just more appeal responses.

For Patient Balances

• At Day 30, send a second statement if no payment has been received. Include the balance due, original service date, and a direct payment link.
• Follow up with an SMS reminder at Day 30 and Day 45. Text messages are read at far higher rates than mailed statements a patient who hasn't opened their billing letter may respond to a text with a payment link within hours.

If reminders haven't produced payment by Day 45, introduce structured options:

• Proactively offer a payment plan for balances over $300. At Day 45–60, introduce a 3- or 6-month installment option. A patient who cannot pay $700 upfront will often readily commit to $235/month. Most patients who carry balances are not avoiding payment they're avoiding a conversation they don't know how to start.
• Send an email statement at Day 45 if text contact hasn't produced a response.

Do not allow the 31–60 bucket to age passively. The 10–15 percentage point drop in recovery rate between this bucket and the 61–90 bucket is driven almost entirely by practices that fail to act during the 31–60 window.

Step 4 How to Recover 61–90 Day AR

Recovering 61–90 day dental AR requires direct patient contact, escalated insurance appeals, and a formal payment plan offer this is your last reliable opportunity for full collection before the 90-day threshold.

Recovery rates in the 61–90 bucket drop to 50–70%. The primary intervention at this stage is direct human outreach not another statement.

For Insurance Balances

• Check the status of any pending appeal filed in the 31–60 window. Insurers are typically required to respond to appeals within 30–45 days in most states. If you have not received a response within that window, call the payer's provider line directly for a status update rather than waiting.
• If an appeal was denied, evaluate whether a peer-to-peer review is available. For claims over $500 denied on medical necessity grounds, requesting a peer-to-peer conversation between the treating dentist and the payer's clinical reviewer often reverses denials that survive the standard written appeal process. Most practices are unaware this option exists or how to request it.

For claims with no resolution yet no denial, no payment, no communication:

• Verify whether the payer's appeal window is still open. If the original denial was processed at Day 20 and no appeal has been filed, you may have 40–160 days remaining depending on the plan. File immediately if the window is still open.
• For claims still pending with no response and no denial escalate to the payer's provider relations department rather than the standard claims line. Provider relations contacts move faster than general claims queues.

For Patient Balances

Make a direct phone call. At this stage, a billing coordinator or better, the office manager should call the patient personally. The framing matters: "We're following up on your balance of [amount] from [date]. We have a couple of options to make this easier can we take a few minutes to figure out what works for you?"

If the patient engages but can't pay in full, present structured options:

• Offer a structured payment plan. Present 3-month, 6-month, and 12-month options explicitly. Patients who carry large balances are more likely to accept an installment arrangement they can plan around than to commit to immediate full payment.
• If the patient does not respond after two direct call attempts, send a formal final notice by mail and SMS stating that the account will be reviewed for collection referral if payment or a payment arrangement is not confirmed within 15 days.

At the end of the 61–90 day window, every account without payment activity or an active payment arrangement should enter the triage process in Step 5. Do not carry these forward for another round of standard follow-up the recovery probability math has changed.

Step 5 How to Recover Aged Dental AR (90+ Days)

Recovering 90+ day dental AR requires triage, not full pursuit. With typical recovery rates of 15–25%, your primary decision at this stage is which accounts to send to a collection agency, which to write off, and which small fraction can still be resolved internally.

At 6 months, per IC System research on dental AR recovery, indiscriminate pursuit costs more in staff time than it recovers across the portfolio see their dental AR benchmarks for full data.

Triage Each Account Before Assigning a Path

Apply this five-step triage process to every 90+ day account before choosing a recovery path:

1. Check balance size against your minimum threshold. Balances under $50 with three or more prior contact attempts have an expected recovery of roughly $10 after staff time is factored in. Write them off and move on.
2. Verify the collection agency sweet spot. Accounts between $50 and $500, aged 90–180 days, where internal recovery has been exhausted, are the ideal profile for collection agency referral. Collection agencies typically charge 25–40% of collected amounts netting $150–$300 on a $500 balance is still a positive outcome.
3. Confirm patient and insurance status. If the patient has filed for bankruptcy, collection is legally restricted. If the patient is deceased, transition to estate billing protocols. These accounts should not enter your standard collection queue.
4. Check the insurance appeal deadline. If the claim aged past the payer's appeal window without a filed appeal, internal recovery is no longer possible. Write it off and note the missed deadline in your billing workflow review.
5. Review patient contact history. A patient who made a partial payment two months ago or has actively communicated about their balance is materially different from a patient with zero contact history. Recent activity even partial payment may extend the collection window under your state's statute of limitations rules.

For Accounts Where Internal Recovery Remains Viable

• A direct call from the practice owner or dentist carries different weight than a coordinator call. For high-value accounts ($1,000+), this contact is worth making personally.
• Consider a settlement offer. Some practices offer 80–90% of the outstanding balance for immediate payment on accounts aged past 90 days. A $900 account settled at $800 today recovers more than a collection agency would net after fees and preserves the patient relationship.

See the Write-Off vs. Collections section below for the specific decision criteria and framework.

Why Insurance AR and Patient AR Need Different Playbooks

Insurance AR and patient AR require entirely separate recovery strategies applying the same workflow to both is one of the most common causes of aged dental AR.

Insurance AR recovery is a documentation and deadline problem.

The payer has the claim. The barrier is a denial reason, a missing attachment, a credentialing mismatch, or a processing delay. Recovery requires identifying the correct denial category, attaching the right supporting documentation, and filing within the payer's appeal window. The limiting factor is almost always time deadlines that are missed cannot be reopened.

Patient AR recovery is a communication and friction problem.

The patient received care and has not paid their portion. The obstacles are typically one of five things: they didn't receive the statement; they don't understand their balance; they can't afford to pay the full amount; they find billing conversations uncomfortable; or they're simply procrastinating.

The operational implication is clear. If your billing coordinator handles insurance denials and patient statements from the same undifferentiated queue, both categories suffer. Assign separate workflows, separate working lists, and separate weekly time blocks for insurance AR and patient AR. For solo practices with one billing staff member, maintain two separate lists and alternate between them but never mix the tactics.

For a full overview of how this split fits into a DSO-level revenue cycle, see our dental revenue cycle management guide for DSOs.

Write-Off vs. Collections: Decision Framework

Use this framework to make consistent, defensible decisions on 90+ day accounts removing the guesswork that delays action and inflates your AR artificially:

The benchmark to monitor: Bad debt write-offs should not exceed 2% of gross production. If your write-offs are consistently above that threshold, the problem is upstream review your dental write-off percentage benchmarks and audit your patient collections process for the systemic gap.

Common Dental AR Recovery Mistakes

Understanding where AR recovery goes wrong is the fastest path to fixing your current situation and preventing the next one.

1. Treating insurance and patient AR as one problem. The tactics, timelines, escalation paths, and success metrics are entirely different. Practices that run a single combined workflow lose effectiveness in both categories. Separate your queues and your protocols.

2. Reviewing the aging report monthly. Monthly AR review is the single most common cause of aged dental AR. A balance that could have been appealed at Day 35 becomes non-appealable by the time it's reviewed at Day 60. The aging report must be worked weekly in the same two-hour block, every week, without exception.

3. Re-filing denied claims without addressing the denial reason. Most first-round denials can be reversed with the correct supporting documentation. Practices that re-submit the same claim without adding the missing narrative, X-ray, or clinical note receive the same denial. Every appeal must specifically address the stated denial reason.

4. Chasing all 90+ day accounts with equal effort. A $38 balance at 120 days costs more to pursue than it will recover at a 20% collection probability. Set a minimum balance threshold ($50 is a common benchmark), apply it consistently, and redirect staff time to balances with meaningful recovery value.

5. Not offering payment plans proactively. Most patients who carry a balance do not ask for a payment plan because they don't know it's available. Proactively offer installment options at Day 45 and again at Day 75 you will convert more accounts than if you wait for patients to request an arrangement that they may not know exists.

6. Missing the peer-to-peer review option. For high-value claims denied on medical necessity grounds, requesting a peer-to-peer review between the treating dentist and the payer's clinical reviewer is frequently more effective than a written appeal. This option is underused because many billing teams aren't aware it exists or how to request it through payer provider relations.

7. No defined write-off authority. When write-off decisions require informal approval or are handled inconsistently, accounts sit in limbo for months counted as AR but with zero recovery probability. Define a clear policy, assign authority, and apply it on a regular schedule.

How Automation Prevents AR From Aging

The most effective AR recovery strategy is upstream prevention stopping balances before they cross 30 days. In 2026, two workflow failures drive most dental AR: eligibility errors at intake and patient billing friction.

Automation addresses both at the source.

Eligibility Verification at Intake

The most common preventable driver of aged insurance AR is an eligibility mismatch discovered after the claim is submitted wrong coverage information, inactive member ID, or incorrect group number. Verifying insurance before treatment is delivered eliminates these denials before they enter the billing cycle.

Arini's AI receptionist handles this automatically during inbound scheduling calls collecting the patient's insurance provider, member ID, and group number and verifying eligibility in real time for supported payers. That information pushes directly into your PMS so your billing team submits accurate claims from day one.

24/7 Billing Inquiry Handling

Patients who have questions about their balance often call after business hours. When they reach voicemail, many defer the payment conversation indefinitely and the balance ages. An AI receptionist that answers billing questions, explains payment options, and processes payments around the clock removes the friction that turns a 30-day balance into a 90-day balance.

Arini handles routine billing inquiries automatically in full HIPAA compliance learn how automating billing inquiries reduces the volume of balances that age past the first bucket. With 300ms response latency, conversations feel immediate and natural patients who call after hours to ask about a balance or make a payment receive the same quality of interaction as a live call. Most patients report they cannot tell they're speaking with AI rather than a staff member, which removes the hesitation that causes billing calls to go unreturned.

Outbound Follow-Up Automation for Aging Balances

Manual AR follow-up is the workflow most likely to slip when the front desk is managing inbound calls, appointments, and patient check-in simultaneously. Arini can run structured outbound follow-up campaigns for outstanding patient balances contacting patients with aging balances, delivering payment reminders, and routing patients who want to discuss their account to a live staff member. This frees your billing team to focus on insurance appeals and high-value account negotiations rather than routine reminder calls.

For balances in the 31–60 day bucket, automated text-to-pay collections significantly outperform paper statements for first-payment conversion by 2026 standards, patients expect a direct link to pay from their phone, with no login required.

For DSOs and multi-location groups running AR campaigns across multiple sites, Arini integrates across all locations simultaneously giving your centralized RCM team consistent patient communication while each location's PMS remains independent.

The goal of automation in AR management is not to replace the billing team, it is to handle the volume of routine outreach that prevents them from focusing on the work requiring professional judgment. Unified Dental Care increased revenue by 12% using Arini; Kare Mobile captured $56K in new patient appointments in month one both by ensuring no patient communication fell through the cracks during or after business hours.

Frequently Asked Questions About Dental AR Recovery

What percentage of dental AR should be over 90 days?

Best-performing dental practices keep AR over 90 days below 3% of total AR, according to dental AR benchmark data. If your 90+ bucket consistently exceeds that threshold, a structured bucket-by-bucket recovery protocol should be your immediate priority.

How do you recover aged dental accounts receivable?

To recover dental accounts receivable systematically, apply a bucket-specific protocol matched to the realistic recovery probability for each age range: prevention and clean claim submission at 0–30 days; denial appeals and billing reminders at 31–60 days; direct patient calls and payment plans at 61–90 days; and triage decisions (collection referral, settlement, or write-off) at 90+ days. Insurance AR and patient AR require entirely separate workflows at every stage.

When should you send dental AR to a collection agency?

The optimal collection agency referral window is 90–180 days after initial billing after internal follow-up is exhausted but before the account ages to near-zero collection probability. Balances between $50 and $500 with an unresponsive patient are the strongest referral candidates. For balances over $500, attempt a direct payment plan or settlement conversation before referring to collections the net recovery after agency fees is often lower than an internally negotiated arrangement.

How long can you collect on a dental insurance claim?

Timely filing limits for initial insurance claims typically range from 90 days to one year from the date of service, depending on the plan. Appeal deadlines after a denial are typically 60–180 days from the date the claim was processed. Missing appeal deadlines forfeits your right to contest the denial which is why weekly AR review and prompt appeal filing are non-negotiable for practices with high claim volume.

How does insurance AR recovery differ from patient AR?

Insurance AR recovery is a documentation and deadline problem the payer has the claim, and resolution requires addressing the specific denial reason with supporting documentation within the payer's appeal window. Patient AR recovery is a communication and friction problem the patient has not paid their balance, and resolution requires multi-channel outreach, payment plan options, and conversations that make payment feasible. Applying the same workflow to both consistently produces poor results in both categories.

When should you write off old dental AR?

Write off dental AR when: the balance is under $50 and three contact attempts have produced no response; the patient is deceased or has filed for bankruptcy; the insurance appeal window has closed with no payment received; or the balance has had zero payment activity for 12+ months. Bad debt write-offs should not exceed 2% of gross production if yours are running higher, the issue is upstream in your patient collections process. Compare your practice against top-quartile performers using dental write-off percentage benchmarks.

How often should you review the dental AR aging report?

Weekly not monthly. Monthly review is the most consistent predictor of aged AR accumulation. A balance that is still within the insurance appeal window at Day 35 may be past deadline by the time it's reviewed at Day 60. Assign a standing two-hour weekly block for AR review and treat it as a non-negotiable part of the billing workflow.

What causes dental accounts to go 90+ days past due?

The most common causes are: insurance denials that were received but not appealed; patient statements delayed or sent to the wrong address; patients who didn't understand their balance or weren't aware of payment plan options; billing staff without enough time to run consistent weekly follow-up; and missed insurance appeal deadlines caused by reactive rather than proactive billing workflows. Most 90+ day balances are preventable with earlier action.

How do you do a dental AR cleanup?

A dental AR cleanup starts with pulling a complete aging report separated by insurance and patient balances, then triaging systematically from oldest to newest. Begin with 90+ day accounts apply the write-off and collection referral criteria above to each one before adding any to a follow-up queue. Then move to 61–90 and 31–60 day buckets with their respective protocols. A focused team working exclusively on aged claims re-submitting with corrected information, filing appeals, and contacting unresponsive patients can recover significant revenue within 30–60 days. After the cleanup, implement weekly AR review to prevent the backlog from rebuilding.

What is a good AR ratio for a dental practice?

A dental practice with healthy AR holds less than 15% of total AR over 60 days and less than 3% over 90 days, with a net collection rate of 98% or higher. The AR-to-production ratio total outstanding AR divided by one month of gross production should be 1.0 or below. Ratios above 1.5 indicate significant collection inefficiency. If your 90+ day bucket consistently exceeds 3% of total AR, a structured bucket-by-bucket recovery protocol is the immediate priority.

Next Steps

Working dental AR by aging bucket with a specific protocol for each stage and a clear write-off decision framework is what separates practices that maintain a consistent 98%+ net collection rate from those writing off more than they should.

The sustainable path to reducing aged AR is upstream: accurate insurance verification at intake, prompt patient statements, and consistent outreach before balances cross the 60-day line. For dental practices, DSOs, and multi-location groups where the front desk team doesn't have the bandwidth to run that outreach consistently because they're managing inbound calls, scheduling, and patient check-in at the same time Book a Demo to see how an AI receptionist handles billing inquiries, runs outbound follow-up campaigns, and frees your team to focus on the insurance and high-value collection work that requires professional judgment.

Related resources:

• Dental AR Over 90 Days Benchmarks
• Dental Collection Rate Benchmarks
• Dental Write-Off Percentage Benchmarks