01
Where to find the code and why it matters
The notice number sits in the upper-right corner of the first page — CP followed by digits for computer-generated notices, or the word Letter followed by digits for letters generated by a person or a specific IRS function. The code identifies the stage: a balance was assessed, a return is missing, a figure was questioned, or enforcement is about to begin. Two letters can look almost identical and carry completely different deadlines, so the code, not the tone of the letter, is what you read first.
02
Balance-due notices: CP14, CP501, CP503, CP504
CP14 is the first bill. It says a return was filed or an assessment was made and money is owed, and it starts interest and failure-to-pay penalties running. CP501 and CP503 are reminders — same balance, firmer language, no new legal rights. CP504 is the turn: it is a Notice of Intent to Levy, and it allows the IRS to seize a state tax refund and signals that a final notice is coming. None of these four is the last warning, but CP504 is the point where a plan should already be in motion.
03
Final notices: LT11, Letter 1058, and CP90
LT11, Letter 1058, and CP90 all say the same thing in different formats — Final Notice of Intent to Levy and Notice of Your Right to a Hearing. Each starts a 30-day window to file Form 12153 and request a Collection Due Process hearing. Filing within that window pauses levy action and moves the case to Appeals. Miss it and the IRS may levy wages and bank accounts, and you are left with the weaker equivalent hearing. These three codes are the ones to act on the day they arrive.
04
Return and examination notices: CP2000, CP3219A, CP59, CP63
CP2000 is not an audit. It means the income reported on your return did not match what employers or banks reported, and it proposes a change with a 30-day response window. CP3219A is the Statutory Notice of Deficiency — the ninety-day letter — and it is the only chance to petition the U.S. Tax Court before the tax is assessed. CP59 says a required return was never filed. CP63 says a refund is being held because of an unfiled year. Each has a different fix, but all of them get worse when ignored, because the IRS will eventually file a substitute return with no deductions.
05
Lien, business, and identity notices
Letter 3172 gives notice that a federal tax lien has been filed and grants 30 days to request a hearing. Letter 1153 proposes the Trust Fund Recovery Penalty against an individual for unpaid payroll taxes and carries a 60-day protest window. CP takes on payroll matters through CP161 and CP162 for unpaid balances and late partnership or S-corporation filings. Letters 5071C and 4883C are identity-verification letters and are not bills at all — they simply hold a refund until you confirm you filed the return.
06
Notices that are not emergencies
Not every envelope is a threat. CP49 says a refund was applied to an older balance. CP12 and CP11 say the IRS corrected math on your return, one in your favor and one against it. CP71 and CP71C are annual reminders of a balance already in a hold or payment plan. Letter 4364C confirms an amended return was processed. These still deserve a read, because they often reveal an old balance or an error worth correcting, but they do not start a clock.
