Timely Filing Limits Guide
Every payer gives you a deadline to submit a claim, and missing it by a single day usually turns the whole balance into a write-off. This guide explains the Medicare rule, the state Medicaid patchwork, typical commercial contract windows, and the proof that saves a claim when a payer says you filed late.
A timely filing denial is money lost to the calendar, not to a coding error: the claim either reached the payer by the deadline, with proof, or it did not. Unlike a medical-necessity denial, there is usually no clinical argument that reopens it, and the balance typically becomes a provider write-off that cannot be passed to the patient. Yet deadlines are among the least standardised rules in billing — Medicare, each state Medicaid program, and every commercial contract run their own clock. Filing late is also a recurring pattern in our roundup of the common reasons claims get rejected.
What the timely filing clock actually measures
Three details decide almost every dispute. First, the clock runs from the date of service — for inpatient stays, usually the discharge date — not from the day you created or sent the claim. Second, the deadline is a receipt deadline: the claim must be received and accepted into the payer's system by the last day, so a claim your clearinghouse rejected two days before the deadline and you fixed two days after it is, in the payer's eyes, late. Third, the limits are contractual and regulatory, so payer systems apply them automatically — the denial usually arrives with reason code CO 29, 'the time limit for filing has expired', and very little room for negotiation. Your real deadline is therefore always earlier than the payer's — leave buffer for rejections and resubmissions.
Medicare: December 31 of the following calendar year
Original Medicare's rule is the most generous and the most misunderstood. Claims must be filed no later than December 31 of the calendar year following the year of service. For services furnished from January through September, that means between roughly 15 months (for a late-September service) and 24 months (for an early-January one) to file. Services furnished from October 1 through December 31 are treated, by rule, as if they were provided in the following year, so their deadline is December 31 of the year after that — up to about 27 months after the date of service. There is no shorter '12-month' Medicare deadline, a persistent myth, and no extension for being busy or short-staffed. Medicare recognises narrow exceptions — an administrative error by Medicare or its contractor, or retroactive entitlement — but each must be documented, and none rescues a claim that simply sat in a workqueue.
Medicaid: fifty states, fifty filing windows
Medicaid has no national filing deadline. Each state sets its own limit in its provider manual, and the range is wide: some states allow a full 12 months from the date of service, while others require claims within 180 days, 120 days, or even 90 days. Managed Medicaid plans add a second layer, because the plan's contract with the provider can set a shorter window than the state's fee-for-service rule — and the contract is what gets enforced. Retroactive eligibility is the recurring trap: a patient who gains Medicaid coverage months after a visit restarts a clock that may already have run most of its course; some states measure from the eligibility determination date instead, but only if you know to ask. The only safe procedure is to check the manual for every state you bill and treat the shortest plan deadline as the working deadline.
Commercial payers: read the contract, not the rumour
For commercial insurance, the filing limit lives in the provider agreement, and it is almost always shorter than Medicare's. Typical contracted windows run from 90 to 180 days from the date of service: 90 days is common with several national payers, others allow 120 or 180, and a minority allow a full year. Out-of-network claims sometimes carry a different window than in-network claims under the same logo. Two contract details matter as much as the headline number: whether the clock runs from the date of service, the discharge date, or the end of the month of service, and whether corrected claims and appeals carry their own deadlines (they usually do, and run shorter than staff expect). Because contracts are renegotiated, verify against the current agreement before relying on any figure, including the examples above.
TRICARE and VA community care
TRICARE is comparatively clear: claims must generally be filed within one year of the date of service, or of the discharge date for inpatient care, with limited exceptions. VA community care is murkier — claims route through regional third-party administrators whose filing deadlines are commonly shorter, often around six months, and are set by the administrator rather than by a single VA rule. For both, confirm the current deadline with your regional administrator before the first claim, not after the first denial.
Secondary claims: a second clock that sometimes resets
Coordination of benefits complicates the calendar. A secondary payer cannot be billed until the primary has decided, and many payers recognise this by measuring the secondary deadline from the date on the primary payer's remittance or explanation of benefits rather than from the date of service — commonly a defined window, such as 60 to 180 days after the primary decision. Others do not reset the clock at all, and simply expect the primary claim to have been filed early enough to leave room. Either way, the primary remittance becomes a filing document: keep it attached to the secondary claim record, because if the secondary payer later alleges late filing, the primary decision date is your defence. Slow primary claims are doubly dangerous — they consume both payers' windows at once.
What counts as proof of timely filing
When a payer denies a claim as late and you believe it was filed in time, documents decide the dispute, not memory. The evidence payers accept, in rough order of strength:
- Clearinghouse or payer acceptance reports — the acknowledgment (such as a 277CA or payer claim-status record) showing the payer accepted the claim, with claim number and date. A report showing you sent a file to the clearinghouse is weaker; payer acceptance is the standard.
- Electronic submission logs tying the specific claim — patient, date of service, charges — to a batch the payer acknowledged.
- Certified mail receipts and return receipts for the shrinking number of paper claims; ordinary postage proofs are rarely accepted.
- The primary payer's remittance for secondary claims, proving the primary decision date from which the secondary clock ran.
Assemble this proof as you bill, not after the denial: acceptance reports are far easier to retrieve within weeks than a year later, when clearinghouse retention may have lapsed.
After a timely filing denial: check, then appeal with paper
Start by verifying the denial is even right. Compare the payer's received date against your acceptance report; confirm the claim denied is the original and not a corrected claim whose original was timely; and check the payer applied the correct plan's deadline — in-network and out-of-network clocks are confused more often than payers admit. If the claim was timely, appeal inside the payer's appeal window (a separate, usually shorter deadline) with the acceptance report as the first exhibit; our denial codes explained guide shows how CO 29 and its companion codes appear on a remittance. If the claim was genuinely late, the remaining options are narrow — documented payer or clearinghouse error, retroactive eligibility, or a contract exception — and the balance otherwise follows your write-off policy. Prevention beats all of it: an aging worklist reviewed by deadline rather than by balance, the habit at the core of our AR follow-up strategies and of the deadline tracking built into our accounts receivable management service, exists so that no claim's last filing day arrives unnoticed.
Frequently asked questions
What is the deadline for filing a Medicare claim?
Medicare claims must be filed by December 31 of the calendar year following the year of service. Services provided from January through September therefore get between about 15 and 24 months. Services provided from October 1 through December 31 are treated as if furnished in the following year, so their deadline is December 31 of the year after that — up to roughly 27 months. There is no separate 12-month Medicare deadline, and extensions are limited to documented exceptions such as administrative error or retroactive entitlement.
Can we bill the patient if a claim is denied for timely filing?
In almost all cases, no. Timely filing is the provider's contractual obligation, not the patient's. Under Medicare rules a beneficiary cannot be charged because the provider filed late, and commercial provider agreements treat timely filing denials as a provider write-off for the same reason. Billing the patient anyway risks contract violations and compliance findings. The narrow exceptions — for example, delays caused by the payer's own error or retroactive eligibility changes — should be documented before any patient balance is considered.
What should we keep as proof that a claim was filed on time?
Keep the payer or clearinghouse acceptance report — the acknowledgment showing the claim was accepted into the payer's system, with the claim number and acceptance date — together with the submission log that ties the individual claim to that batch. For paper claims, keep certified mail receipts and the signed return receipt. For secondary claims, keep the primary payer's remittance, because the primary decision date is what the secondary filing clock usually runs from. Store these records when the claim is billed, not after a denial arrives.