Revenue cycle

Small balance write-offs in medical billing: when to chase a short payment and when to let it go

"Small balance write-off" covers two different things. Writing off a small patient balance is a compliance question with federal rules behind it, while writing off a small payer short-pay is a money question governed by your contract. Either way, the threshold in your practice management system is a policy, whether anyone wrote it down or not.

Patient balance, payer short-pay or credit balance?

Sort the balance before deciding anything. The rules differ by who owes the money.

Small patient balances: the rules that apply

The civil monetary penalty rules define "remuneration" to include waiving coinsurance and deductible amounts. A waiver falls outside that definition only if it isn't advertised, the practice doesn't waive routinely, and the waiver follows a good-faith finding that the patient is in financial need or a failure to collect after reasonable collection efforts (42 CFR 1003.110).

OIG's 1994 Special Fraud Alert on routine waivers explains why. A provider that routinely waives Medicare copayments "is misstating its actual charge." Its example: a $100 charge with the copayment waived is really an $80 charge, so Medicare pays $80 when it should pay $64. The alert adds that routine waivers can implicate the anti-kickback statute, that the financial hardship exception "must not be used routinely," and that otherwise "a good faith effort to collect deductibles and copayments must be made" (OIG).

A policy that tracks the rule bills the patient first and writes off a small remainder only after a documented collection effort or a finding of financial need, applied the same way across payer classes. This is a compliance area. Have counsel review the policy before you adopt or change it.

What CR 2174 does and doesn't say

Many write-off policies cite CMS Change Request 2174 as permission to write off balances under $10. It's a 2002 program memo to Medicare intermediaries about audits of hospital bad debt. It told auditors to skip reviewing hospitals' policies for small debit balances under $10, while disallowing the entire bad debt claim when the hospital hadn't billed the patient for the deductible or coinsurance, and disallowing small remainders written off before a collection effort of at least 120 days from the first bill. It took effect October 1, 2002 and says it "may be discarded after May 30, 2003" (CMS Transmittal A-02-043).

Medicare bad debt sits in Part 413, the principles of reasonable cost reimbursement. Allowable bad debt must come from deductible and coinsurance amounts on covered services, after reasonable collection efforts (42 CFR 413.89). Neither the regulation nor the memo addresses payer short-pays, and the memo doesn't authorize physician practices to write off anything.

Secondary payer short of the coinsurance

When Medicare is primary and a commercial secondary pays less than the Medicare coinsurance, the unpaid part is Medicare cost-sharing. In a 1999 statement to the Practicing Physicians Advisory Council, OIG said coordination-of-benefits terms that routinely leave Medicare copayments unpaid can operate as routine waivers, and that "the obligation to pay the Medicare copayment is a requirement of the Social Security Act." OIG called its conclusions tentative and based on incomplete information (OIG). Don't auto-adjust these; flag them for counsel.

Don't move the shortfall to the patient

On an assigned Medicare claim, you accept the approved amount as the full charge and may collect from the patient only the difference between that amount and Medicare's payment, which means the deductible and coinsurance (42 CFR 424.55(b)). A payer's underpayment is the payer's to correct. For commercial plans, read the contract's hold-harmless and balance-billing terms before billing a patient for anything beyond their cost-sharing.

Small credit balances are not write-offs

A credit balance can mean the practice was paid twice or paid too much. A Medicare overpayment must be reported and returned by the later of 60 days after it's identified or the date any corresponding cost report is due (42 CFR 401.305(b)). A threshold that sweeps credits under $5 into income is a different and riskier policy than one that clears small debits, and it deserves its own approval.

Small payer short-pays: how a threshold becomes policy

An auto-adjust rule in the PM system is a decision to accept the payer's number whenever the remaining balance is below the threshold. It applies to every claim from every payer until someone changes it. Nobody sees the total, and the payer has no reason to fix a rate it loaded wrong.

Short-pays also hide easily. The shortfall often lands inside the CO-45 contractual adjustment on the 835 (see CO-45), and if the write-off is posted as contractual too, it makes your net collection rate look better than it is. You can't size a shortfall without first knowing the expected reimbursement for the line.

A decision method

1. Pattern or one-off? Group short lines by payer and code, and by place of service and modifier where they affect the rate. A repeated shortfall usually means a wrong loaded rate, and one rate-correction request can fix past and future claims. Work patterns regardless of the size of each line.
2. Recoverable value against cost to work. Recoverable value is the shortfall times the number of claims still inside the window, adjusted for how likely recovery is. Cost is staff minutes times your loaded cost per minute, plus any filing fee. Use your own numbers.
3. Is the window still open? For Medicare, a redetermination is due within 120 calendar days of receiving the initial determination, with receipt presumed 5 days after the notice date (42 CFR 405.942). Contractors must handle clerical errors as reopenings, and a party may request a reopening within 1 year of the initial determination for any reason (42 CFR 405.980(a)(3), (c)(1)). For commercial and Medicare Advantage contracts, the contract or provider manual sets the window. Once it closes, the decision has been made for you.

A worked illustration

Illustrative numbers, not real rates. Assume a loaded biller cost of $30 an hour ($0.50 a minute), 15 minutes to appeal one claim, and 2 hours to prepare a rate-correction request covering a pattern.

• One-off. A single line is $6 short. Working it costs 15 × $0.50 = $7.50, more than the shortfall. Log it to the variance code and let it go.
• Pattern. The same code from the same payer is $6 short on 40 claims a month. Over a 120-day window that's about 160 claims and $960 already at stake, plus $2,880 a year going forward if the rate isn't fixed. Working it costs 2 hours × $30 = $60. Chase it, using an underpayment appeal letter.

Under a $10 auto-adjust rule, both lines are written off. Only a variance log tells them apart.

Writing the policy

• Separate thresholds for patient debits, payer debits and credit balances.
• Patient write-offs only after documented collection effort or a documented finding of financial need.
• Payer short-pays posted to a variance adjustment code, not to "small balance" or contractual, so they can be added up.
• A monthly report of variance by payer and code.
• A named person who approves exceptions.
• A yearly review of each threshold against what it actually costs to work a balance.

Adjustment codes

Write-off adjustment codes are internal to your PM system, and you define them. Use distinct ones for patient small balances, payer variance and credit-balance refunds. The claim adjustment reason code on the 835 line is the payer's explanation of its own adjustment. It isn't your write-off code, and posting your write-off under it erases the difference between what the payer did and what you decided.

Questions

Is it legal to write off small patient balances?

Federal rules target routine waivers. Under 42 CFR 1003.110, waiving Medicare coinsurance or deductibles is not prohibited remuneration if the waiver isn't advertised, isn't routine, and follows a good-faith finding of financial need or a failure to collect after reasonable collection efforts. Have counsel review any policy that writes off patient balances.

Can I write off what the secondary insurance didn't pay?

If the primary is Medicare and the secondary paid less than the Medicare coinsurance, the remainder is Medicare cost-sharing. OIG has raised concerns that arrangements which routinely leave Medicare coinsurance unpaid can work as routine waivers, so take these to counsel rather than adjusting them off by threshold.

What small balance write-off threshold should we use?

No regulation sets one for physician practices. Set it from your own cost to work a balance, and set separate thresholds for patient balances and payer short-pays. Credit balances need their own handling because some are overpayments that must be returned.

Can a small short-pay still be appealed after it's written off?

Yes, as long as the appeal or reopening window is still open. A write-off is an entry in your own system and doesn't change the payer's determination. The deadline that started with the remittance is what controls.

Last reviewed October 28, 2026. This guide is general information about payer payment rules, not legal advice. Your payer contract and provider manual control the details; check them before you file.