Notice Of Deficiency

Last reviewed: May 2026

Notice Of Deficiency is usually a notice of deficiency with a deadline that can affect your right to challenge the tax before assessment.

Handle this IRS notice

This page explains the proposed-change notice in plain English and points you to the official IRS help pages before you decide how to respond.

Find official IRS notice help Open appeal rights overview Open review workspace

Keep every page and the mailing date because timing controls the response strategy.

How this notice usually works

What it usually means

This is usually a statutory notice of deficiency.

Why you usually got it

The IRS generally sends this type of notice when it proposes additional tax and is moving toward formal assessment.

What to do first

Note the deadline immediately, compare the notice to your records, and decide whether to agree, dispute, or petition Tax Court.

Time-sensitive note

Deficiency notices are driven by strict deadlines.

Who this is for

People looking for a clearer, calmer path through this tax issue.

When to use this page

Use this page when you need a practical next step, not just a definition.

What to gather

Relevant income records
Statements, receipts, or notices
Tax-year-specific forms if needed

Forms that may matter

Forms depend on the page topic

Step-by-step

Use the summary to decide if this page matches your situation.
Gather the records listed here before making a tax decision.
Follow the step-by-step actions and move into the related tool or next page.

Official sources

Sources and authority

Sources 2/2 Good source coverage Updated May 2026

IRS

TaxHackAI Help Center

Authority source

Action plan

Notice response checklist

Use the dashboard to keep the notice, supporting records, and your review steps connected before you answer or pay.

Checklist progress

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Do first

Note the deadline immediately, compare the notice to your records, and decide whether to agree, dispute, or petition Tax Court.

Watch the deadline

Deficiency notices are driven by strict deadlines.

Understand the issue

The IRS generally sends this type of notice when it proposes additional tax and is moving toward formal assessment.

Use these tools

Find official IRS notice help Open appeal rights overview

Use TaxHackAI

Keep the IRS notice and your records together. Work from the due date and issue code first. Use review to mark anything that still needs proof.

Check authority

This page currently shows 2 sources.

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