Methodology

How we research, source, and verify

Tax content has unique correctness stakes — the wrong number, the wrong form, the wrong appeal window can put a taxpayer in a worse position than ignoring the notice entirely. We treat the editorial process as load-bearing.

Primary-source first doctrine

Procedural facts on this site come from one of four authorities only: irs.gov (the IRS's own detail pages, forms, publications, and IRM), congress.gov or law.cornell.edu (for the Internal Revenue Code), ecfr.gov (for Treasury Regulations), and the U.S. Tax Court's own published procedure. Secondary sources — TaxCure, IRSMind, CPA-firm content blogs, news articles — are useful for framing but never cited as authority for procedural specifics.

When the IRS detail page for a notice and a secondary source disagree, the IRS detail page wins. When the IRS detail page and the underlying statute disagree, we surface the conflict rather than picking one and hoping for the best.

No fabrication policy

If the IRS detail page does not state a specific day count, form number, or statute citation, we say so explicitly. The most common pattern is a notice whose IRS detail page reads "by the date shown on your notice." The fixed day count for that notice is on the individual mailed notice itself, not on the detail page. We render that as "see your notice for the date printed at the top" — never as an invented day count.

For statutory windows referenced by the IRS detail page (e.g., CDP timing under IRC §6320 / §6330, Tax Court 90-day petition window under IRC §6213(a), math-error abatement window under IRC §6213(b)), we cite the statute or the cited Publication directly. The IRS detail page often points to Publication 1660 or Publication 5 rather than restating the window — and we follow that pointer rather than synthesizing.

Last-verified pins

Every per-notice page shows a "last verified" date pin. That date is when the row was last cross-checked against the irs.gov detail page. IRS notice procedures change rarely — but they do change (e.g., the introduction of CP508C passport certification under IRC §7345, the addition of CP3219N for non-filer statutory deficiencies, the rollout of CP220J for ACA Employer Shared Responsibility Payments). We re-verify on a recurring cadence and update the date.

When a row is more than 90 days stale, we flag it for re-verification before it appears on a high-traffic page. The site-wide last-verified pin in the header shows the most recent global review pass: 2026-05-09.

What we omit on purpose

The 50-code canonical list of IRS notices is shorter on this site than some content sites suggest. The reason is simple: we only include codes that have a documented IRS detail page we could verify. Letter 525, Letter 566 (audit), Letter 1153, Letter 226-J, Letter 105C, and Letter 106C — all of which real taxpayers do receive — are not currently included because, at our last verification pass, no irs.gov detail page existed at the expected slugs. We'd rather omit a row than guess at its content. As IRS publishes detail pages for additional codes, we'll add them.

The privacy / architecture pillar

Methodology is incomplete without the privacy architecture. For the decoder itself: pasted notice text never leaves your browser. The decoder runs entirely in the JavaScript shipped with the page. There is no hidden upload, no telemetry on pasted content, no shadow data path. See how our decoder works for the architecture diagram and the network-tab verification instructions.

For our affiliate practice: we exclude tax-resolution-mill operators with active FTC consent decrees, state Attorney General actions, or BBB pattern complaints from any affiliate slot. The exclusion holds even if their payout is highest in the niche. The audience for an IRS-notice site is anxious and high-intent; misleading framing would be a permanent trust loss.

Reviewer engagement

For YMYL-tax content, an external reviewer with a verifiable credential (CPA license + state, EA enrollment number, state bar admission) is the right E-E-A-T signal. As of 2026-05-09, our reviewer engagement is in progress. The About page shows the placeholder we will replace with the reviewer's name, credential, state, LinkedIn, and last-verified date as soon as the engagement closes. We will not list a fabricated reviewer.