Updated August 7, 2026. Quick answer: a state tax notice is not the same animal as an IRS notice, and the differences that matter are who sent it, what stage it represents, and how long you have to disagree. 🔴 Most state notices that arrive are adjustment or determination notices — the stage where the number is still arguable.
The three stages, and why the stage decides everything
1. We changed something. A return-change or adjustment notice: the state recalculated and is telling you the result. 2. We propose to assess. The state believes more is owed and is giving you a stated window to protest before it becomes final. 3. It is now due. The assessment is final and a balance exists.
⚠️ The protest window lives at stage 2, and it is the one people miss — because a proposed assessment reads like a bill and gets treated like one.
California
Notice of Tax Return Change (FTB 5818) — California corrected your return. The two-character code at the bottom of each paragraph is the actual content of the notice, and FTB publishes the table. Also hiding in that table: the four-year and one-year limits on any later claim for refund.
FTB’s own notices and letters index lists the rest alphabetically and numerically, and names its most-searched: FTB 4502 (additional documentation required, refund pending), FTB 4601 and FTB 4684/4685 (demand for tax return), and FTB 5818.
New York
Request for Information (Form DTF-948 / DTF-948-O) — not a bill and not an assessment: New York is holding your refund until you prove something you already claimed. Two things make this letter unusually manageable: the Department tells you to “locate the form number in its bottom-left corner” to identify which letter you actually have, and you can usually read it online before it arrives in the mail.
🔴 The pattern across both states
California hides the meaning in a code at the bottom of the paragraph; New York hides the identity in a form number in the bottom-left corner. In both cases the useful information is in the smallest print on the page, and in both cases the agency publishes the key for free. That is the single most transferable habit in this wing: find the identifier before you read the prose.
⚠️ What is not here yet
Illinois, Pennsylvania and Michigan are reachable and not yet decoded here — each publishes notice guidance in less centralised form than California or New York. Each will be added only when its official notice text can be quoted rather than summarised — the same rule the Medicare decoders follow. A state whose notices lack public documentation gets an honest row here, not a page.
What these pages do and do not do
These decoders explain what a notice says, what stage it represents, and what deadline it carries. They do not decode collection instruments — warrants, levies, liens, garnishment — and they do not advise on paying, settling or negotiating a balance. Where a notice carries a protest or appeal right, that window is part of understanding the notice and is stated exactly.
Sources
California material from the Franchise Tax Board notices and letters index, retrieved 7 August 2026. Federal counterparts: the IRS notices index.