Balance due & the collection ladder

CP521 notice — for your files

The monthly reminder for your installment agreement: how much you owe, how much to pay this month, and where to send it.

Routine

What this letter is

The monthly reminder for your installment agreement: how much you owe, how much to pay this month, and where to send it.

Why you got it: You're on a payment plan; the IRS sends this every month the plan runs.

What it is not

Not a default notice and not a warning — unless the amount or the balance looks wrong, in which case it's your early signal.

Your first move: Pay the monthly amount by its due date. If the balance shown doesn't match your records, call before the next cycle — small errors are cheap here and expensive at CP523.

Your deadline, counted

The clock on this letter: Pay each month by the due date printed on the reminder.

The reminder's own due date controls your monthly payment. Miss one and the next notice in this family is CP523 — intent to terminate.

Your options, in the order most people should try them

1. Pay as billed

Direct debit avoids the missed-payment failure mode entirely.

2. Pay more

Shortens the plan and the interest bill.

3. Flag a mismatch now

Balances that creep instead of shrink usually mean a payment wasn't credited — catch it here.

Your rights on this letter

  • You can pay extra any month — no prepayment penalty — and every extra dollar cuts interest.
  • You can ask to modify the agreement if your income drops, before you miss a payment.

How to respond

Pay online or with the voucher in the reminder.

Scam check

The IRS does not text payment links for CP521. Pay only through IRS.gov or the voucher.

If you ignore it

A missed payment defaults the agreement: CP523 follows, then termination, then the levy ladder resumes.

Where this sits on the ladder: CP523 →

Included in the $39 IRSLetterDecoded Kit

  • The full response letter pack for this notice family
  • What to send — and what to NEVER send
  • The penalty-relief scripts and the payment-plan reality pages
  • Certified-mail proof discipline, start to finish

Get the Kit — $39, one time

One payment. No subscription. Yours to keep — every notice, every letter, every script.

Sources, checked 2026-10-19:
  • IRS — payment plan / installment agreement pages