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when can i amend my tax return

You can usually amend a tax return, but the deadline and rules depend on whether you mean a UK Self Assessment return (HMRC) or a US federal return (IRS).

When you can amend a UK Self Assessment return (HMRC)

For UK Self Assessment, you normally have a 12‑month window after the original filing deadline to amend an online or paper return.

  • You can correct most mistakes (missed income, wrong expenses, allowances, etc.) online through your HMRC account or by sending another paper return.
  • For the 2023–24 tax year, the return deadline is 31 January 2025, so you’d usually have until 31 January 2026 to amend it.
  • If HMRC sent you the notice to file late, the amendment window can extend to 15 months from the date of that notice.

If you miss the amendment deadline but still need to fix something, you must write to HMRC instead of using the normal online amendment route, and you may need to rely on overpayment relief or HMRC’s error‑correction powers.

Example: You file your 2023–24 return on time, then realise months later you forgot some freelance income. As long as it’s before 31 January 2026, you can log in and amend the figures, and HMRC will recalculate what you owe or any refund due.

When you can amend a US federal tax return (IRS – Form 1040‑X)

In the US, the IRS lets you amend an individual return using Form 1040‑X , and the time limit mainly matters if you want a refund.

  • You generally have 3 years from the original filing deadline to file an amended return to claim a refund.
  • Alternatively, you have 2 years from the date you actually paid the tax for that year, if that date is later; the IRS uses whichever date is later.
  • Filing earlier than the deadline does not shorten the 3‑year window; it still runs from the official due date (typically around 15 April).

You use Form 1040‑X when you need to change important items like filing status, dependents, income you forgot to report, or deductions/credits you missed—not minor clerical errors the IRS can fix on its own.

Example: You filed your 2024 US return by 15 April 2025 and later discover a missed education credit. You’d normally have until about April 2028 to amend and claim any extra refund, assuming you paid on time.

Quick pointers before you amend

  • Check which system you’re under (HMRC vs IRS) and follow that authority’s deadlines and forms.
  • Gather your original return, corrected figures, and supporting records before you submit changes, so your story is consistent if they ask questions.
  • If your amendment window has passed or your situation is complex (multiple years, big income changes, penalties risk), it’s wise to speak with a qualified tax adviser in your country.

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Wondering when can I amend my tax return? Learn the key deadlines and rules for changing UK Self Assessment returns and US IRS Form 1040‑X filings, plus what to do if you miss the window.

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