The IRS sends a letter by certified mail when something on your account carries a legal deadline, when collection action is about to start, or when the agency needs to confirm your identity before processing a return. The reason you would receive an IRS certified letter almost always falls into one of those three categories, and the notice or letter number printed in the upper-right corner tells you which one. That number, and the mailing date next to it, are the two pieces of information that matter most in the first five minutes after you open the envelope.
First, Confirm the Letter Actually Came From the IRS
The IRS starts most contact with taxpayers through the U.S. Postal Service, not email, text messages, or social media.1Internal Revenue Service. How to Know It’s the IRS A legitimate notice always shows a notice or letter number (something like CP14, 5071C, or Letter 3219), your taxpayer identification number, and a specific tax year.
If something looks off, sign in to your IRS Online Account at irs.gov. Digital copies of most notices appear under “Notices and Letters,” so you can compare what arrived in the mail against what the IRS actually sent.2Internal Revenue Service. Online Account for Individuals – Frequently Asked Questions You can also look up the notice number on irs.gov to see what that type of letter covers, or call the IRS at 1-800-829-1040.
Reason 1: A Notice of Deficiency Proposing More Tax
A Notice of Deficiency, often called the “90-day letter,” is the most consequential reason the IRS uses certified mail. Letter 3219 is the version most individual taxpayers see. It means the IRS finished reviewing your return and is proposing changes that would increase what you owe.3Taxpayer Advocate Service. Letter 3219, Notice of Deficiency The IRS cannot simply assess the extra tax without first giving you a chance to challenge it in the U.S. Tax Court, and this letter is that chance.
You have 90 days from the mailing date on the notice to file a petition with the Tax Court. If you live outside the United States or the notice is addressed to a foreign address, the window is 150 days.4Office of the Law Revision Counsel. 26 USC 6213 – Restrictions Applicable to Deficiencies; Petition to Tax Court The clock starts on the date printed on the notice, not the day you pick it up from the post office. Sit on the envelope for two weeks and you have burned two weeks of the deadline.
Miss the window and the consequences are heavy. The IRS assesses the additional tax and starts collection. From that point, your only path to challenge the amount is to pay it in full and then file a refund claim, which is far slower and more expensive than petitioning the Tax Court while you still can. If the letter in your hand is Letter 3219 or another Notice of Deficiency, this is the deadline that matters more than any other.
Reason 2: Collection Warnings — Levy and Lien Notices
If you have an unpaid balance that has gone unresolved, the IRS escalates through certified mail before taking your property.
Notice of Intent to Levy (Letter 1058 or LT11)
This notice warns that the IRS plans to seize property to satisfy the debt. That can include bank accounts, wages, Social Security benefits, vehicles, and in some cases a home.5Internal Revenue Service. Understanding Your LT11 Notice or Letter 1058 You have 30 days to pay the balance, arrange a payment plan, or request a Collection Due Process hearing with the IRS Independent Office of Appeals.6Taxpayer Advocate Service. Notice of Intent to Levy Do nothing and the IRS can begin seizing property once that window closes. A timely CDP hearing request, filed on Form 12153, pauses collection while the hearing is pending.7Internal Revenue Service. Request for a Collection Due Process or Equivalent Hearing
Notice of Federal Tax Lien Filing (Letter 3172)
This letter tells you the IRS has placed a legal claim against everything you own, now and in the future, to secure the debt. A lien does not take your property the way a levy does, but it attaches to all of it. Federal tax liens no longer appear on credit reports from the major bureaus, but they remain public records that lenders and other creditors can discover, and they complicate selling or refinancing real estate.8Taxpayer Advocate Service. Letter 3172 – Notice of Federal Tax Lien Filing and Your Right to a Hearing Under IRC 6320 Letter 3172 also triggers the right to a CDP hearing.
Reason 3: Identity Verification
Not every IRS certified letter means you owe money. The CP5071 series, which includes the commonly seen 5071C letter, means the IRS flagged a return filed under your Social Security number or Individual Taxpayer Identification Number and needs you to confirm your identity before it will finish processing the return.9Internal Revenue Service. Understanding Your CP5071 Series Notice This often happens when the IRS suspects someone else may have filed a fraudulent return using your information.
The notice will direct you to verify online at irs.gov/verifyreturn or by calling the number on the letter. Have the notice, the return for the year in question, a prior-year return if you can find one, and any W-2s or 1099s in front of you before you start. If you did file the return, verification clears the hold and processing continues. If you did not file it, the verification process itself lets the IRS know someone used your information, and you will not need to file a separate identity theft affidavit unless the IRS specifically asks for one.
Other Reasons the IRS Uses Certified Mail
Some in-person audit notifications arrive by certified mail, particularly when strict documentation deadlines apply. Final Determination Letters, issued after the IRS appeals process concludes, are also sent by certified mail because they set the final terms of your case and start separate court-petition clocks.
The Mailing Date Is What Counts, Not the Day You Read the Letter
The deadline on an IRS certified letter runs from the date the IRS mailed the notice, not the date you received it or opened it.4Office of the Law Revision Counsel. 26 USC 6213 – Restrictions Applicable to Deficiencies; Petition to Tax Court Every day between that mailing date and the day you actually read the letter counts against you. Pick up certified mail promptly.
If the last day of your deadline falls on a Saturday, Sunday, or a legal holiday in the District of Columbia, you get an automatic extension to the next business day.10Office of the Law Revision Counsel. 26 USC 7503 – Time for Performance of Acts Where Last Day Falls on Saturday, Sunday, or Legal Holiday Beyond that narrow exception, the IRS cannot extend a statutory deadline like the 90-day Tax Court period. No amount of calling or writing changes it.
Some people assume that refusing to sign for certified mail, or leaving it unclaimed at the post office, keeps the IRS from acting. It does not. The IRS only needs to prove the notice was mailed to your last known address, which is the address on your most recently filed and processed return, cross-referenced with the U.S. Postal Service’s National Change of Address database.11Federal Register. Definition of Last Known Address Telling your bank or employer about a move does not count as notifying the IRS. You need to file a return with the new address or submit Form 8822.12Internal Revenue Service. About Form 8822, Change of Address If a Notice of Deficiency goes to that address and you never pick it up, the 90-day clock still runs, the tax gets assessed when it expires, and collection begins.
What to Do the Day the Letter Arrives
Open it the same day. Find the notice or letter number in the upper-right corner and read the entire document before reacting. The letter identifies the tax year, the issue, any dollar amount involved, and the deadline for responding.
Write down the deadline and mark it on a calendar. If it is a 90-day letter, set a reminder at least two weeks before the actual date. Gather every document tied to the tax year in question: the filed return, W-2s and 1099s, receipts for deductions, and any earlier IRS correspondence about the same issue. If the notice references specific line items, pull the records that back up your original numbers.
For notices involving significant amounts, audit findings, or proposed levies, think about hiring a tax professional. An Enrolled Agent, CPA, or tax attorney can represent you before the IRS and often catches errors in the IRS’s own calculations. The cost is almost always less than accepting an incorrect assessment or losing appeal rights by missing a deadline.
When you send a written response, be specific: identify the notice number, the tax year, and each adjustment you are contesting. Attach copies, never originals. Send it by certified mail so you have proof of the postmark date, which counts as your filing date under the timely-mailing rule.13Office of the Law Revision Counsel. 26 USC 7502 – Timely Mailing Treated as Timely Filing and Paying Keep copies of everything you send and receive, and log the date, time, and name of any IRS representative you speak with by phone.
If you agree you owe the balance, the IRS offers a short-term payment plan of up to 180 days with no setup fee, and a long-term installment agreement with setup fees starting at $22 for online applications paid by direct debit.14Internal Revenue Service. Payment Plans; Installment Agreements An active installment agreement stops new liens and levies and keeps the debt from being certified as seriously delinquent for passport purposes.
What Ignoring the Letter Actually Costs
Penalties and interest keep running on unpaid balances. The failure-to-pay penalty is 0.5% of the unpaid tax for each month it remains outstanding, capped at 25%, and it rises to 1% per month starting 10 days after the IRS issues a notice of intent to levy.15Internal Revenue Service. Failure to Pay Penalty If you also failed to file the return, a failure-to-file penalty adds another 5% per month with its own 25% cap.16Internal Revenue Service. Failure to File Penalty Interest compounds on top of that.
Ignore a levy notice and the IRS can seize bank accounts, garnish wages, and take other property without a further warning letter. Ignore a Notice of Deficiency and the proposed tax is assessed by default; you lose the ability to challenge the amount in Tax Court without first paying everything the IRS says you owe.
For larger debts the stakes climb. If your total unpaid federal tax liability exceeds $66,000 (adjusted annually for inflation), the IRS certifies it as seriously delinquent tax debt and notifies the State Department, which can deny a new passport application, refuse to renew an existing passport, or revoke a current one.17Internal Revenue Service. Revocation or Denial of Passport in Cases of Certain Unpaid Taxes That certification does not happen while you have an active installment agreement or a pending CDP hearing.18Office of the Law Revision Counsel. 26 USC 7345 – Revocation or Denial of Passport in Case of Certain Tax Delinquencies Responding on time is what keeps those doors open.