CSED Calculator

By Forrest Baumhover, CFP®, EA · Last verified October 23, 2026

Collection Statute Expiration Date, with every tolling event shown.

The CSED Calculator computes the Collection Statute Expiration Date: the date, ten years after the IRS formally records a tax as owed (the assessment), when its power to collect by levy (seizing wages, bank funds or property) or lawsuit ends (IRC §6502(a)(1)). It serves practitioners first; a taxpayer can check a date against their transcript.

What this tool does, and what it does not

It adds ten years, then each period you enter when the law stopped the clock, then the time the law keeps the clock stopped after each event ends:

Bankruptcy: six more months after the IRS may collect again (IRC §6503(h)(2)).
Offer in compromise or installment agreement request: 30 more days after a rejection, longer during a timely appeal, and none after a withdrawal (IRC §6331(k)(1), (2)).
Terminated installment agreement: 30 days after the termination, longer during a timely appeal (IRC §6331(k)(2)).
Innocent spouse request: 60 more days (IRC §6015(e)(2)).
Collection Due Process (CDP) hearing: no expiration until at least 90 days after the final determination or after the IRS receives the taxpayer's written withdrawal of the hearing request (IRC §6330(e)(1); Treas. Reg. §§301.6320-1(g)(1), 301.6330-1(g)(1)).
Time abroad: no expiration until at least six months after the taxpayer returns (IRC §6503(c)).
Military deferment: 270 more days after service ends (50 U.S.C. §4000(c)).

Where events overlap, the calculator counts each shared day once, as the IRS does: overlapping suspensions run concurrently, not cumulatively (IRM 5.1.19.3(2)). Enter each event's dates. If you extend an end date by the added time, the calculator counts that time twice.

It has no entry for a TC 550, which extends the CSED to a date the IRS enters (IRM 5.1.19.2.3), and no event for litigation or a suit to reduce the tax to judgment (IRM 5.1.19.3.2), court custody of assets (IRC §6503(b)), estate tax extensions (§6503(d)), wrongful seizure or lien (§6503(f)), combat zone service (IRC §7508) or a Form 911 request to the Taxpayer Advocate (IRC §7811(d)), whose suspension the IRS does not code (IRM 5.1.19.3.13). It cannot see a suspension the transcript does not show, and it trusts the dates you enter for time abroad.

How to use it

Enter the assessment date: the TC 150 date for the original return, or the TC 290 or TC 300 date for a later assessment, which carries its own CSED (IRM 5.1.19.2.1). For a substitute for return the IRS prepared, use its deficiency assessment date (IRM 5.1.19.3.15).
Add each suspension event with its own start and end dates. These transcript codes mark them:

Bankruptcy: TC 520 with closing code 60–67, 83 or 85–89, ending at the matching TC 521 (IRM 5.1.19.2.2). Document 6209 defines closing code 81 as litigation; IRM 5.1.19.3.1.1 also lists it with bankruptcy and suspends the CSED from the TC 520 date to the TC 521 date plus six months, so enter a closing code 81 freeze that a TC 521 closed as a Bankruptcy event too.
Offer in compromise: TC 480 to TC 481, TC 482 or TC 780. That span already includes the 30 days after a rejection (IRM 5.1.19.3.4.1), so choose "TC 481, 482 or 780 date from the transcript" as how it ended.
Installment agreement request: TC 971 action code 043 to TC 971 action code 063 or TC 972 action code 043 (IRM 5.1.19.3.5.1), not the months the agreement ran, which suspend nothing (IRM 5.1.19.3.5). A termination posts as TC 971 action code 163.
CDP hearing: TC 520 closing code 76 (lien) or 77 (levy) (IRM 5.1.19.3.3.1), ending when the hearing's determination, including any court appeal, becomes final or the IRS receives the taxpayer's written withdrawal (IRM 5.1.19.3.3; Treas. Reg. §§301.6320-1(g)(1), 301.6330-1(g)(1)). An equivalent hearing does not stop the clock.
Innocent spouse request: TC 971 action code 065 (IRM 5.1.19.3.6.1); the suspension runs until the spouse files a waiver, the 90-day window to petition the Tax Court closes, or a Tax Court decision becomes final, "plus, in each instance, 60 days" (IRM 5.1.19.3.6).
Military deferment: TC 500 closing code 51, for the period of service (IRM 5.1.19.3.9). Closing codes 52, 54, 56 and 58 mean combat zone service instead (IRM 5.1.19.3.8).
Time outside the United States (no transcript code): a continuous absence of six months or more (IRC §6503(c)).

Check "Still pending" for an open event; the calculator counts it through today and marks it provisional.

The rule behind it

A suspension stops the clock for a period the law sets, usually while the law bars collection. A waiver extends the date by agreement, only in the two cases IRC §6502(a)(2) allows: an installment agreement, or a levy released after the ten years end.

Worked example

Suppose an account transcript shows TC 150 dated 04-15-2024, TC 520 closing code 85 dated 06-01-2025 and TC 521 dated 03-01-2026. Closing code 85 marks a bankruptcy (IRM 5.1.19.2.2). Enter April 15, 2024 as the assessment date and one Bankruptcy event from June 1, 2025 to March 1, 2026. IRM 5.1.19.3.1.1 runs a bankruptcy suspension from the TC 520 date to the TC 521 date "plus six months," following IRC §6503(h)(2), so the suspension runs to September 1, 2026. The calculator returns:

Base CSED: April 15, 2034.
Days added: 457.
CSED: July 16, 2035.

When to call a practitioner

The computed CSED has passed or falls less than six months from today. Confirm it against IRM 5.1.19.2 and 5.1.19.3 before anyone relies on it.
The transcript shows a TC 550, or the taxpayer signed a Form 900 waiver.
Only one spouse on a joint return filed the bankruptcy, offer, CDP, installment or innocent spouse request. The IRS may need a separate CSED for each spouse (IRM 5.1.19.3.1.1 through 5.1.19.3.6.1).

Common Questions

How do I calculate an IRS CSED?

Take the assessment date, add ten years, then add every day the clock stood suspended, including the time the law adds after each event, and count a day that two events share once. The calculator does this for the events you enter.

Does an IRS audit stop the CSED clock?

No. The ten years run from an assessment (IRC §6502(a)(1)), and an audit assesses nothing until it ends. If it ends in a new assessment, that amount gets its own ten-year CSED from its own date (IRM 5.1.19.2.1, TC 300).

Does filing a Tax Court petition stop the CSED?

Not for tax already assessed. A notice of deficiency (the IRS letter proposing more tax) stops the IRS's time to assess that deficiency through the petition period, or, if the taxpayer petitions, until the Tax Court decision becomes final, plus 60 days (IRC §6503(a)(1)). The existing balance's clock keeps running. A CDP appeal (IRC §6330(e)(1)) and an innocent spouse petition (IRC §6015(e)(2)) do stop a running CSED.

More from the Desk

Download the CSED Calculator Compliance Card (PDF) — to record your firm’s review of this tool

Need help with your specific situation?

This tool gives you the numbers and the citation, but every case has details a calculator can’t weigh. For a second opinion from a tax professional, email Forrest directly. Do not email Social Security numbers, account numbers, or other sensitive information. An email creates no client-practitioner engagement; case-specific advice starts only after both parties have mutually accepted terms and payment has been made.

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Sources

Read the Deep Dive behind this tool: Deep Dive: The Complete IRS Collections Timeline