IRS procedures you must know cold: notices, Tax Court, statutes, and refunds

The rules, one page each

1. Tax Court after a deficiency notice: 90 days from mailingContrasting cases

   A taxpayer may petition the U.S. Tax Court without first paying only after the IRS mails a valid notice of deficiency and only if the petition is filed within 90 days of the mailing date (150 days if the notice is addressed to a person outside the United States). The 90/150-day period runs from mailing, not receipt.

2. 30-day letter vs notice of deficiency vs math error vs CDPSort it

   A 30-day letter offers administrative Appeals. A statutory notice of deficiency opens a 90-day (U.S. address) or 150-day (foreign-addressed) prepayment Tax Court petition. A math-error notice allows a 60-day abatement request to force deficiency procedures. A Final Notice of Intent to Levy allows a 30-day request for a CDP hearing.

3. IRC 6501 assessment: compute the 3-year deadlineWorked example

   Under IRC §6501(a), the IRS generally has 3 years after a return is filed to assess. A return filed before its due date (including a valid extension) is deemed filed on that due date, while a late return starts the period on the actual filing date; an amended return does not restart it.

4. 6-year IRS assessment for >25% omission of gross incomeStep by step

   If the return omits from gross income an amount exceeding 25% of the gross income stated on the return, the IRS has 6 years to assess. The period runs from the deemed filing date: the due date if filed early or on time, or the actual filing date if filed late. Exactly 25% does not qualify.

5. Refund claims: timeliness and the 3‑year lookback when relying on withholding and estimatesWorked example

   A refund claim is timely if filed by the later of 3 years after the return filing date or 2 years after payment. The amount refundable is limited to tax paid within the applicable lookback period: generally 3 years (plus any extension period) before the claim date. Withholding and estimated taxes are deemed paid on April 15 of the following year.

6. Refund claims with mixed payments: when the 2‑year lookback limits you to later paymentsWorked example

   If a claim is not filed within 3 years of the return filing date, it can still be timely within 2 years of payment, but the refundable amount is then limited to tax paid within the 2 years before the claim. Payments with a late return or later assessments often fall inside; older withholdings usually do not.