IRS Notice Codes (CP / LT) Explained: What They Mean + What To Do Next

Use this guide to identify the notice family, understand what it commonly indicates, and take the safest next step without missing deadlines.

More IRS / Tax guides IRS / Tax hub IRS / Tax code directory

TL;DR

✓ Read the notice header and deadline first; timing matters more than the family code.
✓ CP and LT are notice families; the content and tax year determine next actions.
✓ Respond through official channels only; avoid third-party links and numbers.
✓ Keep proof of submission and copies of everything you send.

Quick Navigation

Symptoms Root Causes Step-by-step fixes What NOT to do If it persists Code directory Related guides & hubs FAQ References

Symptoms / When you see this

✓ You receive a letter labeled CP-… or LT-…
✓ The notice references a tax year and a response deadline.
✓ Your refund status changes after the notice.

Root causes (grouped)

✓ Return processing questions and mismatches.
✓ Identity verification requests.
✓ Refund holds or offsets.
✓ Audit or review notices.
✓ Balance due or payment-related notices.

Step-by-step fixes (safe, prioritized)

✓ Read the deadline and requested action first.
✓ Confirm the tax year and taxpayer ID referenced.
✓ Use only official IRS response methods printed on the notice.
✓ Keep copies and proof of delivery/submission.
✓ If you disagree, respond with clear documentation and factual corrections.

What NOT to do

✓ Do not ignore deadlines.
✓ Do not share sensitive data through unverified links.
✓ Do not assume a notice means fraud; verify via official account tools.

If it persists (escalation checklist)

✓ Gather: notice copy, tax return copy, W-2/1099 data, transcripts if available.
✓ Follow identity verification steps only through official channels.
✓ Consider a tax professional for complex disputes.

Code directory within this guide

✓ Notice meaning depends on the tax year and the notice text. Use linked pages as a plain-language map and confirm using the notice itself.

Code	Meaning	Next step
CP12 notice	Math error correction notice — This notice indicates that the IRS corrected a mathematical or clerical error on the return.	Follow the checklist on the code page
CP05 notice	Refund under review notice — This notice indicates that the IRS is reviewing the return and additional time is required before issuing the refund.	Follow the checklist on the code page
CP14 notice	Balance due notice — This notice indicates that a balance is due on the tax account.	Follow the checklist on the code page
CP21 notice	Amended return adjustment notice — This notice indicates that the IRS processed an amended return and adjusted the account accordingly.	Follow the checklist on the code page
CP24 notice	Refund offset notice — This notice indicates that all or part of the refund was applied to an outstanding obligation.	Follow the checklist on the code page

Tip: If your exact code isn’t listed, use the closest hub link above and browse related prefixes or message patterns.

FAQ

Is a CP notice always bad?

Not always. Some notices are informational, while others require action. The deadline tells you what matters.

How do I verify a notice is real?

Use official IRS account tools and contact methods printed on the notice. Avoid unverified links or phone numbers.

Should I respond online or by mail?

Follow the notice instructions. Some require online verification; others require mailed documents.

What if the notice is wrong?

Respond with documentation and factual corrections. Keep proof of submission.

Will a notice delay my refund?

Commonly yes when verification or review is required. The notice usually explains next steps.

What should I keep for records?

The notice, your response, supporting documents, and proof of delivery/submission.

Do CP/LT notices guarantee an audit?

No. Audit language is typically explicit. Many notices are routine processing/verification.

Should I call immediately?

Only when the notice instructs it or online tools cannot clarify. Documentation-based responses are often more effective.

References / Notes

✓ The IRS notice itself
✓ IRS account tools
✓ Official IRS publications and instructions