Timely Filing Limits by Payer (2026): Deadlines You Can’t Afford to Miss

Every payer gives your practice a strict window to submit a claim — miss it, and the entire visit’s revenue vanishes with one of the few denials that has almost no appeal. The timely filing limit by payer ranges from as little as 90 days for many commercial plans to a full year for Medicare, and your contract’s deadline is the one that controls. This 2026 guide lays out the limits payer by payer, why CO-29 denials are so expensive, how to track deadlines operationally, and what to do when the clock is about to run out. Getting claims out the door on time is one of the most basic jobs of medical billing services — and one of the easiest to let slip.

What Is a Timely Filing Limit in Medical Billing?

A timely filing limit is the maximum time a payer allows between the date of service and the date it receives your claim. Submit inside the window and the claim processes normally; submit one day late and the claim is denied with adjustment code CO-29 — “the time limit for filing has expired” — regardless of how clean or medically necessary the claim was. Three things make this limit different from other billing rules. First, it’s measured from the date of service, not from when you realized the claim existed. Second, every payer sets its own limit — there is no universal standard. And third, your provider contract’s deadline overrides any number you read online, so published limits are a starting point for tracking, never the final word.

Why Are Timely Filing Denials (CO-29) So Expensive?

CO-29 is one of the few denials that is nearly unfixable after the fact, and it carries a financial sting other denials don’t:

• Almost no appeal rights. A late-filed claim is dead on arrival — the payer never evaluates the merits. Medicare explicitly states that late-filing denials are not appealable; the only narrow exceptions are administrative errors by CMS or retroactive eligibility, handled as reopenings, not appeals.
• You cannot bill the patient. The group code “CO” (Contractual Obligation) means the delay was the provider’s responsibility, not the patient’s. Balance-billing a patient for a missed deadline violates most payer contracts and is restricted by law in many states — so the full charge becomes a write-off.
• The loss is 100% of the claim’s value. A coding denial can be corrected and rebilled; a CO-29 on an expired claim is typically gone forever. One missed Medicare claim worth $2,500 costs more than most practices’ entire monthly billing software bill.

That’s why timely filing deserves its own guardrails in the revenue cycle: unlike most denials, this one has no second act. Practices that run a disciplined AR recovery process still prioritize claims by their remaining filing window — because an old claim with no deadline left isn’t recoverable at all.

Timely Filing Limits by Payer: 2026 Deadline Table

Here are the commonly published filing windows for major payers as of 2026. Treat these as planning baselines — always confirm the exact limit in your provider contract and the payer’s current provider manual, since plan type, network status, and state can change the number.

Payer	Standard Filing Limit	Key Notes
Medicare (Parts A & B)	12 months (365 days)	Federal rule (42 CFR 424.44); measured from date of service. Medicare Advantage plans set their own, shorter windows.
Medicaid	Varies by state: 90 days to 12 months	Each state program sets its own limit; check your state Medicaid provider manual. MCOs often enforce 90-day windows.
UnitedHealthcare	90 days (commercial, in-network)	Some contracts allow up to 180 days; 365 days for Medicare Advantage. UHC’s commercial appeal window can be as short as 65 days — check your Participation Agreement.
Aetna	~120 days (commercial)	Varies by plan and contract; some allow up to 365 days. Out-of-network windows are typically longer.
Cigna	90 days (in-network); 180 days (out-of-network)	Employer-sponsored plans can vary; some allow up to 1 year.
Humana	90 days (commercial)	365 days for Medicare Advantage. Humana has largely exited the employer-group commercial business, so most claims now run under MA or Medicaid rules.
Blue Cross Blue Shield	Varies by state: 90 days to 1 year	Each independent Blue plan sets its own window (e.g., ~90 days in some Anthem states, 1 year in others). Verify with your local affiliate.
Tricare	12 months (some plans 180 days)	Active-duty claims may carry different windows — verify.
Workers’ Compensation	30–180 days by state	Often the shortest deadlines in billing; some states allow as few as 30 days.
Auto / No-Fault	30–90 days by state	Among the strictest; state-specific rules control.

The pattern is clear: commercial claims cluster in the 90–180 day band, while Medicare, Tricare, and most Medicaid programs allow up to a year. The danger claims are the short-window ones — a UnitedHealthcare commercial claim has roughly one-quarter of Medicare’s grace period, so it needs to be at the front of every work queue.

What Causes Claims to Miss Their Filing Deadline?

Claims don’t miss deadlines by accident — they miss them because something upstream stalled them. The most common causes:

1. Slow charge entry. Encounters that sit un-coded for weeks are the single biggest driver. If your providers take 7–14 days to close notes and coders take another week, a 90-day window is already one-third gone.
2. Credentialing delays. Claims held because a new provider isn’t yet credentialed with the payer can age past the window while enrollment drags on. The claim’s clock keeps ticking during credentialing — payers rarely pause it.
3. Eligibility and COB errors. Claims billed to the wrong payer, or held for coordination-of-benefits information, burn calendar days while they sit in “waiting for info” status.
4. Clearinghouse and EDI failures. Rejected claims that nobody reworks, or batches that fail silently, can age unnoticed. A claim the clearinghouse never accepted is a claim that was never filed.
5. Secondary claims queued behind primaries. Practices that batch secondary claims weekly or monthly lose weeks of the secondary payer’s window after the primary EOB posts.

Notice the pattern: every one of these is a process failure, not a payer failure. That’s good news, because process failures can be engineered out.

How Can You Track Filing Deadlines Before They Expire?

A deadline you can’t see is a deadline you’ll miss. The practices with the lowest CO-29 rates run an explicit, daily filing-deadline workflow:

1. Load every payer’s limit into your practice management system. Don’t keep deadlines in a spreadsheet on one person’s desktop. Enter the contract filing window per payer (and per product line — commercial vs. Medicare Advantage) so the system can calculate a “file-by” date on every claim automatically.
2. Set alerts at 30, 15, and 7 days before expiration. Tiered warnings give the billing team escalating urgency: 30 days means “work this queue,” 15 days means “escalate to the manager,” 7 days means “submit today, no exceptions.”
3. Run a weekly “at-risk” worklist. Every Monday, generate a list of unbilled charges and unpaid claims sorted by days remaining — not by dollar amount. A $200 claim with 10 days left outranks a $2,000 claim with 200 days left.
4. Reconcile submissions against clearinghouse acceptances. “Sent” is not “filed.” Require a 277CA or EDI acceptance report for every batch, and auto-flag any claim with no acceptance within 48 hours.
5. File secondary claims immediately. Don’t batch them. Submit secondary claims the same day the primary remittance posts — the secondary payer’s clock is already running.
6. Audit the unbilled-encounter queue daily. Any encounter older than 3 business days without a charge on it should be visible to management. The filing window starts at the date of service, not at charge entry.

What Should You Do When the Filing Deadline Is About to Expire?

When a claim enters the final 30 days of its window, normal workflows are too slow. Switch to rescue mode:

• Submit the clean claim immediately — even if supporting documentation is still coming. A claim filed on time without an attachment can often have documentation appended; a claim filed late is denied outright. File first, supplement second.
• Confirm receipt, not just submission. Call the payer or check the portal to verify the claim is in their system with a received date inside the window. Keep the acceptance proof — it’s your only ammunition if CO-29 appears anyway.
• Know the exceptions that can buy time. Medicare allows late filing for administrative errors by the government, retroactive entitlement, and certain disasters; some commercial contracts grant extensions for retroactive eligibility or payer-caused delays. Document the exception at the time — reconstructing it months later rarely succeeds.
• If CO-29 already hit, check for proof before you write it off. If you have a clearinghouse acceptance or payer-received timestamp inside the window, appeal with that proof attached — timely-filing appeals succeed only with documented evidence of on-time receipt. Without proof, write the claim off promptly and route the root cause to your prevention workflow.
• Bill the correct secondary or correct payer fast. If the original filing went to the wrong payer, the clock with the right payer may still have time — submit there immediately rather than appealing the wrong-payer denial.

FAQs

What is the timely filing limit for Medicare in 2026?

Medicare requires claims no later than 12 months (365 calendar days) from the date of service, under federal regulation 42 CFR 424.44. Medicare Advantage plans are different — they set their own windows, typically 90–180 days.

Can a timely filing denial (CO-29) be appealed?

Rarely. CO-29 appeals succeed only with proof the claim reached the payer inside the window — typically a clearinghouse 277CA acceptance or payer-received timestamp — or with a documented exception such as retroactive eligibility. Without that proof, the denial stands and the claim must be written off.

Can you bill the patient if a claim is denied for timely filing?

No. The CO (Contractual Obligation) group code assigns responsibility to the provider, and most payer contracts — plus many state laws — prohibit balance-billing patients for missed filing deadlines. The charge becomes a contractual write-off.

Which payer has the shortest timely filing limit?

Among major payers, commercial plans like UnitedHealthcare (90 days in-network) and some BCBS affiliates (~90 days) have the shortest standard windows. Workers’ compensation and auto/no-fault claims can be even shorter — 30–90 days depending on the state.

Does the filing deadline pause while a claim is being corrected?

No. Corrected claims and resubmissions are generally subject to the same original filing deadline, measured from the date of service. This is why reworking rejections quickly matters — every correction cycle burns days off a clock that doesn’t stop.

Next Steps: Never Lose Another Claim to CO-29

Timely filing is the least forgiving rule in medical billing: the deadlines are hard, the CO-29 denial is nearly unappealable, and the patient can’t be billed for the loss. The practices that beat it don’t work harder — they work with visible deadlines, daily at-risk worklists, and a rescue protocol for the final 30 days. If missed deadlines are already showing up in your write-offs, a review of your submission workflow will usually find the leak in one afternoon. Request a free billing workflow review — we’ll check your filing-deadline tracking, your clearinghouse reconciliation, and your at-risk queues against the standards that keep CO-29 denials near zero.