On the paper
Compare each proposed adjustment against the return, the source documents, and the examination report attached to the letter.
Read the examiner's explanation for each adjustment, not just the numbers in the computation. The explanation states the reason the item was disallowed, and the reason determines what a protest has to answer. An adjustment disallowed for lack of substantiation is answered with records. An adjustment disallowed on a legal ground is not.
Find the date printed on your notice or letter. The paper notice and the current official IRS instructions control, even where this page differs.
Where this notice comes from
Letter 525 is the point where an examination becomes a dispute with a procedure attached. The examiner has finished and has written up the proposed adjustments, and the letter offers Appeals.
Missing the protest window does not end everything, but it changes the route. The IRS then issues a statutory notice of deficiency, and the forum becomes the United States Tax Court within the period section 6213(a) sets.
The size of the proposed adjustment affects the form of the protest the IRS asks for. Smaller cases can use a short written request; larger ones require a formal written protest with specified content.
General next steps
- Go through the report and separate the adjustments you accept from the ones you dispute.
- Follow the letter's instructions for replying and for supplying documents.
- If you disagree, prepare the protest the letter describes and keep proof that you sent it on time.
Timing
The IRS page on letters and notices offering an appeal opportunity, checked September 10, 2026, states that a protest should be filed within 30 days from the date of the letter to appeal. The date printed on the notice controls; do not calculate a deadline from this page.
What Letter 525 does not mean
A 30-day letter is not an assessment and not a bill. Nothing is owed on it yet. It also does not mean the examination is over in any final sense, because the IRS Independent Office of Appeals reviews the file independently of the examiner who wrote the report. What it does mean is that the administrative route is open now and closes when the period runs.
What this page cannot tell you
This page cannot evaluate the merits of an examination adjustment or tell you whether to appeal.
IRS audit defense
This letter involves an IRS examination or a proposed tax adjustment. Read IRS audit defense.
IRS Appeals
This letter may offer review by the IRS Independent Office of Appeals. Read IRS Appeals.
Official sources
- IRS letters and notices offering an appeal opportunity
- Preparing a request for Appeals
- Taxpayer Advocate Service: Letter 525
If anything on this page differs from your notice or from current IRS instructions, follow the notice and the IRS.
Common questions
What happens if I let the 30 days pass?
The IRS moves to a statutory notice of deficiency. That notice sets the period for filing a petition in the United States Tax Court, and the administrative appeal is no longer the route.
Is Appeals the same office that examined my return?
No. The IRS Independent Office of Appeals is separate from the examination function and reviews the file on its own, including the hazards of litigating the position.
Can I send more records instead of protesting?
The letter gives instructions for replying with documents. Supplying what the examiner asked for can resolve a substantiation adjustment without a protest, but the protest period continues to run while that happens.