10 Most Common IRS Notices for Small Businesses (and How to Respond)

The IRS sends ~225 million notices per year. Most aren't audits — they're automated, fixable in writing, and harmless if you respond on time. Here's how to recognize the ones small businesses see most.

How to identify any IRS notice

Look at the upper right corner — every IRS notice has a code:

• CP = "Computer Paragraph" — automated
• LT = "Letter" — manual review or collection
• LTR = letter from a specific function

The notice number tells you exactly what's happening. Below are the 10 most common for SMBs.

CP2000 — Underreporter Notice

What it means: The IRS matched your return to 1099s/W-2s sent by third parties and found a mismatch. They're proposing additional tax.

Severity: Low–medium. NOT an audit.

Response: 30 days. Either agree (pay the proposed tax) or disagree (write a letter explaining with documentation). CP2000 instructions.

CP14 — Balance Due

What it means: You filed but didn't pay. Or paid less than the balance due.

Severity: Low if paid promptly; escalates fast if ignored.

Response: Pay within 21 days, OR set up a payment plan via IRS Online Payment Agreement.

CP501 / CP503 / CP504 — Reminder Series

What they mean: Escalating reminders for unpaid balance. CP501 is the first nudge; CP504 is the "we're about to seize your stuff" warning.

Severity: Low → high (CP504 is serious).

Response: Pay or set up an installment plan. Don't ignore CP504 — next step is Notice of Intent to Levy.

LT11 / Letter 1058 — Final Notice of Intent to Levy

What it means: The IRS will seize wages, bank accounts, or property if you don't respond.

Severity: Critical.

Response: 30 days to file Form 12153 — Request for Collection Due Process Hearing. This stops the levy and gives you appeal rights. Consider hiring a tax pro IMMEDIATELY.

CP2501 — Discrepancy Investigation

What it means: The IRS found a discrepancy but isn't yet proposing changes — they want clarification first.

Severity: Low. Easier than CP2000.

Response: Provide the requested documentation within the deadline (usually 30 days).

CP297 — Notice of Levy on Federal Payments (FPLP)

What it means: The IRS will offset your federal payments (Social Security, contractor payments to feds, etc.) to satisfy unpaid tax.

Severity: High.

Response: 30 days to request a CDP hearing via Form 12153.

CP161 — Request for Tax Return

What it means: The IRS thinks you should have filed but didn't. Could be triggered by 1099s/W-2s with your TIN attached.

Severity: Medium. Can lead to a Substitute For Return (SFR) where the IRS files for you with no deductions.

Response: File the actual return (or explain why you weren't required to file).

Letter 525 — General 30-Day Letter

What it means: The IRS proposes changes after an audit. They give you 30 days to agree or appeal.

Severity: High. This IS audit output.

Response: 30 days. Either sign the proposed changes (Form 870) OR submit a written protest to the IRS Independent Office of Appeals.

Letter 950 — 30-Day Letter (Examination)

What it means: Similar to 525, but for specific types of audits. Same response timeline.

Severity: High.

Response: Engage a CPA or EA. File a written protest if you disagree.

Letter 3164 — Information Document Request (IDR)

What it means: An auditor wants documents related to a specific issue. Often during an active audit.

Severity: Medium-high.

Response: Provide ONLY what's requested. Don't volunteer more. Tax pro is highly recommended.

Universal response framework

For any IRS notice:

1. Open it within 24 hours. Notice deadlines start the day the IRS issued it, not when you opened it.
2. Verify it's real. Scams mimicking IRS notices are common. Real notices come by USPS mail with a CP/LT number, your name, and a reference to a specific tax year. The IRS does NOT call, text, or email first contact.
3. Note the deadline in your calendar.
4. Read it twice. Most notices include the exact response action needed.
5. Pull your return for the relevant tax year so you can verify the IRS's claim.
6. Call a CPA / EA if the proposed adjustment is > $5,000 or you don't understand it.
7. Respond in writing. Phone calls are useful but get everything important documented.

Where to call for help

• IRS Business and Specialty Tax line: 1-800-829-4933 (M-F 7a-7p local)
• Practitioner Priority Line: 1-866-860-4259 (your CPA/EA uses this; faster than the public line)
• Taxpayer Advocate Service: 1-877-777-4778 — free help when you've tried but can't resolve. Run by the IRS but operationally independent. Local TAS office locator.

How Accountaxed reduces notice frequency

Most CP2000s come from 1099 mismatches. Accountaxed tracks every 1099 you issue and every 1099 you receive, reconciles them against your books before filing, and flags discrepancies BEFORE the return goes to the IRS — so the matching algorithm doesn't ding you later.

Run a pre-filing audit → · IRS Notice Lookup