Rules
IRS response deadlines: calendar days, not business days, and when dates move
Most IRS response deadlines count calendar days, not business days. This explains start dates, weekend and holiday moves, postmark proof, and missed dates.
What to take away
- Most IRS response windows run in calendar days. A weekend or holiday matters only when it lands on the final day.
- Section 7503 moves a due date that falls on a Saturday, Sunday, or legal holiday to the next open day.
- When a notice states business days, count Monday through Friday, skip federal holidays, and start the day after the notice date.
- A missed 90-day letter becomes a final assessment, and the Tax Court loses jurisdiction.
- The postmark decides the date, and the receipt is what proves it.
Which IRS office sets the clock
A notice from the IRS names a date, and the count follows the document that mailed it. The unit named on the notice controls where the reply goes. A campus address, an examination group, and the Independent Office of Appeals each receive different filings.
The issuing office also sets the length of the window. A campus unit that mails an automated underreporter notice sets one fixed calendar-day window and prints its own return address.
A field examination group sets its 30-day letter by its own case schedule, so the printed date can differ from a campus letter for the same tax year. Appeals sets a response date tied to its conference calendar and confirms any change in writing.
1 U.S.C. § 1 supplies the base rule: exclude the day of the act, and count the last day unless it is a Saturday, Sunday, or legal holiday.
Business days versus calendar days on a notice
Most IRS letters count calendar days. A 30-day letter gives 30 days from its date, and the reply must be postmarked by the printed date. If the last day is a Saturday, Sunday, or legal holiday, the deadline moves to the next open day.
Calendar vs business day counts
Calendar days
- Weekends
- Counted
- Federal holidays
- Excluded
- 30-day letter
- 30 calendar days
- IDR in LB&I exam
- Not used
- Last-day rule
- Moves to next open day
Business days
- Weekends
- Excluded
- Federal holidays
- Excluded
- 30-day letter
- Not used
- IDR in LB&I exam
- Set by examiner
- Last-day rule
- Moves to next open day
Start with a notice dated Friday, October 3, 2025. Day one is Saturday, October 4. Day 30 is Sunday, November 2, 2025, so the reply is due Monday, November 3. Day 90 is Thursday, January 1, 2026, a legal holiday, so a petition filed with the Tax Court is due Friday, January 2, 2026.
A notice date that falls on a Saturday, Sunday, or legal holiday moves to the next open day under section 7503, and the count starts the day after that. Keep the envelope and the postmark; they settle any argument about which date the period ran from.
For a window you add forward from a notice date, the add business days formula shows how the start convention shifts the answer by a day.
A few IRS steps use business days, and large business examinations often set an information document request window in business days; weekends inside it do not count.
OPM list of federal holidays fixes dates treated as closed. A calendar year holds 260 or 261 weekdays before holidays come out, and any year's workday total narrows that to three possible figures.
What a compliant response contains
A complete reply includes the taxpayer name and identifying number, the notice number and date, the tax period, and a signed statement of what is disputed. Send the records that support your position to the address or fax number printed on the notice.
What a compliant reply includes
- Taxpayer name and identifying number
- Notice number and notice date
- The tax period at issue
- Signed statement of what is disputed
- Supporting records sent to printed address
For a deficiency notice, file the petition with the Tax Court, not the IRS.
| Document | Usual window | Days counted |
|---|---|---|
| CP2000 underreporter notice | 30 days from the notice date | Calendar days |
| Examination report with a 30-day letter | 30 days | Calendar days |
| Notice of deficiency, the 90-day letter | 90 days, or 150 if addressed outside the United States | Calendar days |
| Information document request in a large business exam | Set by the examiner | Business days |
Records to keep while a notice is open
The cutoff is the date printed on the notice. A reply mailed on or before that date is timely, and the postmark, not the day the envelope is opened, decides the date.
The mailbox rule settles most arguments about timeliness. A document mailed on time with a United States postmark, or through a designated private delivery service, is treated as filed on the postmark date. IRS Publication 509 publishes the legal holidays that govern federal tax due dates, and the list is reissued each year. Hold on to the proof:
Proof to keep while notice is open
- The notice and its envelope
- Mailing receipt with legible postmark
- Full copy of response and attachments
- Account transcript for the tax period
What happens if you miss the date
An unanswered notice of deficiency becomes final. The IRS assesses the tax, and the Tax Court loses jurisdiction over the case. Collection can then proceed through a levy on wages or a bank account. A Collection Due Process notice works the same way: the right to court review is lost when the request is late.
A petition filed on day 91 is late. The Tax Court cannot extend the 90-day period, and no later filing brings it back.
Where the rules differ by place
Federal holidays set the count for federal tax, and section 7503 uses the District of Columbia calendar as its reference. State tax agencies publish their own holiday lists, so a state filing date can land on a day the IRS treats as open.
A notice addressed to a taxpayer outside the United States carries 150 days instead of 90. Disaster relief announced under section 7508A can move a deadline for a whole county after a storm or a fire. The boundaries matter: days between dates by country sets out how federal, state, and foreign calendars diverge.
Even within one jurisdiction the answer shifts each January. A federal holiday that falls on a Saturday is observed the Friday before, and one that falls on a Sunday is observed the Monday after. Holidays with verified dates lists the observed dates and a source for each.
