Short answer
Enter the date on your IRS letter and this calculator counts the deadline: generally 30 days for a 30-day letter, and 90 days (150 if addressed outside the US) to petition the Tax Court on a notice of deficiency, moved past weekends and DC holidays. If the notice prints a later last day, that date controls.
Key takeaways
- A notice of deficiency gives you 90 days from its mailing date to petition the U.S. Tax Court, or 150 days if it is addressed to a person outside the United States (IRC 6213(a)).
- If the 90th or 150th day is a Saturday, Sunday or District of Columbia legal holiday, the deadline moves to the next business day; a petition filed by the last day printed on the notice is timely even if that date is later.
- Neither the IRS nor the Tax Court can extend the petition deadline, and talking to the examiner or Appeals does not pause it.
- The 30-day letter deadline is set by the IRS, not by statute: use the response date on the letter and call before it passes if you need more time.
- The IRS generally has 3 years after you file to assess more tax (6 years if more than 25 percent of the income on the return was left out); an early return counts as filed on its due date.
Count your audit deadline
Choose the letter you have, enter the date printed on it, and press the button. For the assessment statute, enter the tax year and the date the IRS received your return. If the letter or notice prints its own deadline, enter it too and the calculator compares the two dates. Nothing you type is sent or saved.
How the calculator counts each date
| Letter or date | Period | How it is counted | Weekend or holiday | Rule |
|---|---|---|---|---|
| 30-day letter (for example Letter 525, 915 or 950) | Generally 30 days | From the date of the letter; the response date printed on the letter governs | No statutory extension; the tool warns you and suggests responding a business day early | IRS practice (IRM 4.10.8; Publication 3498) |
| Notice of deficiency, US address | 90 days | Day 1 is the day after the notice is mailed, so the 90th day is the mailing date plus 90 calendar days | Moves to the next day that is not a Saturday, Sunday or DC legal holiday | IRC 6213(a); IRC 7503 |
| Notice of deficiency addressed outside the US | 150 days | Same count, 150 calendar days | Same rule | IRC 6213(a) |
| Assessment statute, general | 3 years | From the date the return was filed; an early return counts as filed on its due date (April 15 for a calendar-year Form 1040, ignoring extensions) | Not adjusted by the tool | IRC 6501(a), (b)(1) |
| Assessment statute, large omission | 6 years | Same start date; applies if you left out more than 25 percent of the gross income stated on the return | Not adjusted by the tool | IRC 6501(e)(1)(A) |
Weekends and District of Columbia holidays
IRC 6213(a) says the petition period is counted “not counting Saturday, Sunday, or a legal holiday in the District of Columbia as the last day,” and IRC 7503 sets the same next-business-day rule for most tax deadlines. The Tax Court’s petitioner guidance says the same thing: if the last day is a Saturday, Sunday or DC holiday, you have until the next business day. The calculator builds the DC holiday list from the DC Code as the IRS manual lists it (IRM 25.6.1.6.18). A holiday that falls on a Saturday is observed on the Friday before, and one that falls on a Sunday on the Monday after. Inauguration Day counts every fourth year.
| Holiday | 2026 | 2027 |
|---|---|---|
| New Year’s Day | Thu, Jan 1 | Fri, Jan 1 (and Fri, Dec 31, 2027 for New Year’s Day 2028, a Saturday) |
| Dr. Martin Luther King Jr.’s Birthday | Mon, Jan 19 | Mon, Jan 18 |
| Washington’s Birthday | Mon, Feb 16 | Mon, Feb 15 |
| DC Emancipation Day | Thu, Apr 16 | Fri, Apr 16 |
| Memorial Day | Mon, May 25 | Mon, May 31 |
| Juneteenth | Fri, Jun 19 | Fri, Jun 18 (observed) |
| Independence Day | Fri, Jul 3 (observed) | Mon, Jul 5 (observed) |
| Labor Day | Mon, Sep 7 | Mon, Sep 6 |
| Indigenous Peoples’ Day | Mon, Oct 12 | Mon, Oct 11 |
| Veterans Day | Wed, Nov 11 | Thu, Nov 11 |
| Thanksgiving Day | Thu, Nov 26 | Thu, Nov 25 |
| Christmas Day | Fri, Dec 25 | Fri, Dec 24 (observed) |
The 2026 dates match the District of Columbia government’s published list of 2026 legal public holidays. One-off closures, such as a national day of mourning, are not built in; if one falls on your last day, check with the Tax Court or a professional.
Worked examples
Example (assumed dates). These come straight from the calculator.
| Situation | Raw count | Deadline |
|---|---|---|
| Notice of deficiency mailed July 27, 2026 to a US address | Day 90 is Sunday, October 25, 2026 | Monday, October 26, 2026 |
| Notice of deficiency mailed July 14, 2026 | Day 90 is Monday, October 12, 2026, Indigenous Peoples’ Day | Tuesday, October 13, 2026 |
| Notice mailed February 4, 2026 to an address in another country | Day 150 is Saturday, July 4, 2026 | Monday, July 6, 2026 (the Friday observance comes before the last day, so it does not help) |
| 30-day letter dated October 2, 2026 | Day 30 is Sunday, November 1, 2026 | No automatic extra day: have your response arrive by Friday, October 30, or by the date printed on the letter |
| 2025 Form 1040 filed February 10, 2026 | Treated as filed April 15, 2026 | 3-year statute ends April 15, 2029; 6-year period ends April 15, 2032 |
| 2025 Form 1040 filed on extension, October 15, 2026 | Filed October 15, 2026 | 3-year statute ends October 15, 2029 |
A return filed on February 29 has no anniversary in a common year; the calculator then shows March 1 and flags it, so treat February 28 as the safer planning date.
The 30-day letter deadline
A 30-day letter sends you the examiner’s report (usually Form 4549 or 4549-A with an explanation of items) and gives you generally 30 days from the letter’s date to agree, agree in part, or ask for an Appeals conference. The Taxpayer Advocate Service tells recipients of Letter 525 to respond by the due date on the letter, and to call the number on the letter before that date if they need more time. Extensions are a matter of IRS practice, not a right. Our guide to the 30-day letter explains each choice, including the small case request for proposed changes of $25,000 (IRS.gov, 2026) or less per period and the formal written protest above that.
If you let the date pass, the audit is not over and nothing is assessed yet: the IRS generally sends a notice of deficiency next, which starts the 90-day clock below.
The 90-day Tax Court deadline on a notice of deficiency
The notice of deficiency (Letter 3219, CP3219A and similar) is the only notice that lets you take the IRS to the U.S. Tax Court without paying first. Under IRC 6213(a), the petition is due within 90 days after the notice is mailed, or 150 days if it is addressed to a person outside the United States. The Tax Court says it “cannot extend the time for filing a petition in response to a notice of deficiency.”
- The printed date protects you. A petition filed on or before the last date the IRS prints on the notice is treated as timely, even if the statutory count would end sooner.
- E-filing. The Tax Court must receive an electronically filed petition by 11:59 pm Eastern Time on the last day.
- Mailing. A petition received in an envelope with a legible U.S. Postal Service postmark within the filing period is treated as timely; the Tax Court warns that private meter or online postage marks may not prove timely mailing. Under IRC 7502, certified or registered mail gives you proof, and designated private delivery services can also qualify.
- Filing fee. The Tax Court’s fee is $60 (IRS.gov, 2026), and the Court may waive it if you show you cannot pay.
If the amount in dispute is $50,000 (IRS.gov, 2026) or less for each year, you can ask for the small tax case procedure. The full picture, including what the IRS can and cannot do during the 90 days, is in our notice of deficiency guide and the CP3219A explainer.
The 3-year and 6-year assessment statute dates
The audit itself has no legal time limit; the limit is on assessing more tax. Under IRC 6501(a), tax generally must be assessed “within 3 years after the return was filed.” A return filed before its due date is treated as filed on the due date (IRC 6501(b)(1)), and the IRS manual applies this to the date prescribed by law without extensions: a return received on April 13 is deemed filed on April 15, even when April 15 is a Sunday. A return filed late, or on extension, counts from the day it was actually filed.
The period is 6 years if you left out income of more than 25 percent of the gross income stated on the return (IRC 6501(e)(1)(A)). There is no time limit for a false or fraudulent return or when no return was filed (IRC 6501(c)). The calculator does not model three things that can move the date:
- A consent you signed on Form 872 or 872-A extends the period; you can refuse or limit it (IRC 6501(c)(4)). See Form 872 explained.
- A notice of deficiency suspends the period while the IRS is barred from assessing, through any Tax Court case, plus 60 days (IRC 6503(a)).
- The filing date the IRS uses. Your account transcript shows the date the IRS treats as your filing date.
For how long each type of audit tends to run, see how long an IRS audit takes.
If the deadline has passed or is days away
- Find the notice and its printed date. Compare it with the calculator’s date and work from the earlier one.
- If a Tax Court deadline is still open, protect it first. The Tax Court’s petitioner pages explain how to file; Low Income Taxpayer Clinics and the Court’s pro se resources help people who file on their own.
- If a 30-day letter date passed, call the number on the letter. You will usually still get a notice of deficiency.
- If the 90 days passed, the Tax Court route without paying first is generally closed. Audit reconsideration, paying and claiming a refund, and an offer based on doubt as to liability remain; see missed an IRS audit deadline.
You can do all of this yourself, and the Low Income Taxpayer Clinics help eligible taxpayers for free or a small fee. A representative is worth it when the amount is large, several years are involved, or the deadline is days away. Global Gate Tax Relief offers a free consultation and quotes a flat fee upfront if it takes the case: request a review or call 1-877-800-8180.
Frequently asked questions
Start the day after the notice was mailed and count 90 calendar days (150 if the notice was addressed to you outside the United States). If the last day is a Saturday, Sunday or District of Columbia legal holiday, the deadline moves to the next business day. If the notice prints a later last day to petition, that printed date controls.
Yes. All calendar days count, including weekends and holidays. Only the last day is adjusted: if it falls on a Saturday, Sunday or DC legal holiday, you have until the next business day.
No. The Tax Court says it cannot extend the time to file a petition in response to a notice of deficiency, and talking to the IRS examiner or Appeals does not pause the clock. File the petition by the deadline and keep talking afterward.
Do not count on it. The 30-day response date is set by the IRS, not by the statute that governs the Tax Court petition. Use the date printed on the letter, respond before it, and call the number on the letter in advance if you need more time.
New Year’s Day, Dr. Martin Luther King Jr.’s Birthday, Inauguration Day every fourth year, Washington’s Birthday, DC Emancipation Day (April 16), Memorial Day, Juneteenth, Independence Day, Labor Day, Indigenous Peoples’ Day, Veterans Day, Thanksgiving and Christmas. A Saturday holiday is observed the Friday before, a Sunday holiday the Monday after.
An early return is treated as filed on its due date, so for a calendar-year Form 1040 the 3-year period starts on April 15 of the year after the tax year, not on the day you filed. A return filed late or on extension starts the period on the day it was filed.
If the printed last day is later, it controls, because a petition filed by that date is treated as timely. If it is earlier, file by the earlier date to be safe and have a professional check the notice.
Sources
- 26 U.S.C. 6213, Restrictions applicable to deficiencies; petition to Tax Court
- 26 U.S.C. 7503, Time for performance of acts where last day falls on Saturday, Sunday, or legal holiday
- 26 U.S.C. 7502, Timely mailing treated as timely filing and paying
- 26 U.S.C. 6501, Limitations on assessment and collection
- 26 U.S.C. 6503, Suspension of running of period of limitation
- U.S. Tax Court: Starting a case (petitioners)
- IRM 25.6.1, Statute of Limitations Processes and Procedures (incl. 25.6.1.6.15 and 25.6.1.6.18, List of Legal Holidays)
- IRM 4.10.8, Report Writing (30-day letter)
- IRS Publication 3498, The Examination Process
- Taxpayer Advocate Service: Letter 525
- IRS: Low Income Taxpayer Clinics
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