What does your IRS notice mean?

Every IRS notice carries a code in the top right corner. It tells you what the letter actually is — a first bill, a proposed change, or a final warning before a levy — and how long you have to act.

Worth knowing before you start: most IRS notices cannot be answered by fax. Of the notices below only the CP2000 series publishes fax numbers. Everything else uses the phone number or address printed on your own notice, and no third party can change that.

Your notice code

CP503

Second reminder — balance still unpaid

What it means

Your second contact about the same unpaid balance. The IRS warns that inaction can lead to a federal tax lien, which affects your access to credit.

Deadline

The due date shown on the notice.

How to respond

  • Pay in full online or by the enclosed envelope.
  • Apply for an installment agreement if you can't.
  • Call the toll-free number on the notice.

Can you fax it?

Verified 2026-07-19 · Official IRS page for this notice

Notices covered

Code What it is Deadline Fax?
CP14 First bill — you owe unpaid tax The pay-by date printed on the notice. No
CP503 Second reminder — balance still unpaid The due date shown on the notice. No
CP504 Notice of Intent to Levy Immediate — the notice demands payment now. No
LT11
Letter 1058 		Final Notice of Intent to Levy — with hearing rights Contact the IRS immediately. CDP hearing requests run on a 30-day clock from the notice — see the instructions printed on your letter. No
CP2000 Underreported income — proposed changes The date printed on the notice. Yes
CP162 Penalty for not filing electronically Pay by the date shown on the letter to avoid further interest. No
CP261 S corporation election accepted None. Nothing to answer. No
CP575 EIN assigned None. Keep it permanently. No
Letter 12C More information needed to process your return Send the requested information within 20 days. No

Verified against each notice's own irs.gov page on 2026-07-19. Your notice is the authority on your deadline — this table is a guide.

Questions

Top right corner of the first page, printed as CP followed by digits (CP14, CP2000) or LT followed by digits (LT11). Some are worded as letters instead — Letter 12C, Letter 1058.

No. Of the notices covered here only the CP2000 series publishes fax numbers, and even then you must send it to the specific unit named on your notice. For everything else, use the contact details printed on your own letter — that routing is unique to your case.

Use the contact details on the notice itself. Every IRS notice has a matching "Understanding your notice" page on irs.gov, and the deadline that binds you is always the one printed on your copy — not a general rule from any website, including this one.

It depends on the notice. Missing a Collection Due Process window on an LT11 costs you the Tax Court route but an equivalent hearing may still be available within a year. Missing a payment date accrues interest and penalties. Call the number on the notice, or the Taxpayer Advocate Service if you are facing hardship.

No — both are confirmations. CP575 assigns your EIN and CP261 accepts your S corporation election. Neither needs a reply; both should be kept permanently.

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