Tax · United States
IRS Notice CP501 — a reminder that a tax balance is still open
A CP501 is a reminder that a balance is still owed on one of your tax accounts. It is an early step in the IRS collection sequence — it warns that a federal tax lien may be filed, but nothing is being seized yet.
How serious: routineAlso called: CP501, first reminder notice, IRS reminder of unpaid taxes
The IRS sends a CP501 because it has a balance due on record for you. It usually arrives after the CP14 bill; the Taxpayer Advocate Service refers to the CP501 as the '1st Notice' of the reminder series.
The notice repeats the amount owed, the tax year, a due date, payment options and a toll-free number. It also warns that a Notice of Federal Tax Lien may be filed — a public notice to creditors about the government's claim on your assets.
It is an early, routine step. The more serious letters — intent to levy, a final notice with hearing rights — only come later in the sequence, if the balance stays unresolved.
Who sends it
The Internal Revenue Service (IRS) — the United States federal tax authority, part of the Department of the Treasury.
The code 'CP501' is printed in the top corner. The wording runs along the lines of 'Reminder notice' or 'You have an unpaid balance'. The notice states the amount owed, the tax year, a due date, payment options and a toll-free number, and comes with a payment envelope.
The deadline
Pay the amount you owe by the due date shown on the notice
The notice asks for payment of the amount owed by the due date shown on it; that date is counted from the date printed on the notice.
If you do nothing
Interest continues to accrue and additional penalties may apply. The IRS may file a Notice of Federal Tax Lien — a public notice to your creditors that the government has a right to your interests in your current assets and any assets you acquire after the lien is filed — and the collection sequence continues with further notices.
How it escalates
- 01Interest accrues and the failure-to-pay penalty continues.
- 02A Notice of Federal Tax Lien may be filed — a public notice to creditors of the government's right to your current assets; a lien can affect the ability to get credit.
- 03A further reminder, the CP503, is sent because the IRS has not heard from you and a balance remains unpaid.
- 04A CP504 Notice of Intent to Levy follows, allowing levy of a state tax refund after 30 days, then a final CDP notice (LT11/CP90) before levy of wages and bank accounts.
How to respond
Response types
- Confirm paymentPayment of the unpaid balance (Online Account / Direct Pay / check with the payment stub)
- Ask for instalmentsPayment plan / installment agreement (Online Payment Agreement, or Form 9465) · IRC §6159Form: Form 9465 (Installment Agreement Request); Form 433-F where required
- Ask for more timeShort-term payment plan (up to 180 days) · IRC §6159
- File the objectionDispute of the balance (toll-free number on the notice or written correspondence to the campus address; Form 843 for penalty or interest abatement) · IRC §6404 (abatement)Form: Form 843 for penalties, interest and additions to tax; Form 1040-X to correct the return
- Ask for clarificationRequest for explanation of the balance / account transcript requestForm: Form 4506-T for a mailed transcript
Where and how
- U.S. Mail (First-Class Mail)
- Certified Mail / Registered Mail (USPS), return receipt requested
- Designated Private Delivery Service (DHL Express / FedEx / UPS — qualifying service levels only)
- IRS Individual Online Account (irs.gov/account) / Business Tax Account
- Telephone — the number printed on the notice (general line 800-829-1040)
What makes it count
Respond by the due date printed on the notice. Mail is treated as filed on the postmark date under IRC §7502 when properly addressed with postage prepaid; online payments and payment-plan applications count on their transaction timestamp and must actually complete by the due date. Keep proof — certified mail or a designated private delivery service — for anything that may need to be evidenced later.
Common questions
Is the CP501 the same thing as the first bill?
No. The CP501 is a reminder, and it usually arrives after the CP14 bill. The Taxpayer Advocate Service calls it the '1st Notice' of the reminder series.
Does a CP501 mean a lien has already been filed?
No. It warns that a Notice of Federal Tax Lien may be filed if the balance stays unpaid. The notice itself files nothing.
What comes after a CP501 if nothing changes?
A further reminder (CP503), then a CP504 Notice of Intent to Levy, and eventually a final notice with hearing rights before any levy of wages or bank accounts.
Sources
Facts verified against the sources below on 28 August 2026.