U.S. · IRS letters
IRS Letter 2800C explained.
A letter to an employer about an employee’s Form W-4 (a lock-in letter).
Letter 2800C goes to an employer and says the IRS believes an employee may have filed an incorrect Form W-4. The IRS page says to begin withholding income tax from that employee’s wages at the rates in the letter, effective 60 days from the date of the letter. It is an employer letter, not an individual taxpayer’s notice.
Compare IRS letters and notices
Result
IRS letters and notices at a glance
| Letter or notice | What the IRS page says it is | Response, as the IRS page states it |
|---|---|---|
| Letter 12C | The IRS needs more information to process your individual income tax return: missing or corrected forms or schedules, verification of income, withholding and credit amounts, or verification of taxpayer identification numbers or Social Security numbers. | Send the information requested within 20 days. Respond even if you disagree, with a clear explanation. Do not file Form 1040-X. |
| Letter 4464C | Verifying your income and income tax withholding on a return. | If you filed a return, no action is needed. Do not call until 60 days after the letter date, and only if you have not received your refund or heard from the IRS by then. |
| Letter 4800C | The IRS is proposing a change to your tax return. | Complete and return the Response Form within 30 days from the date of the letter. If you disagree, reply with supporting documentation. |
| Letter 4883C | The IRS received a Form 1040-series return filed under your SSN or ITIN and needs you to verify your identity and the return to continue processing it; if you didn’t file one, you must let the IRS know. | Call the Taxpayer Protection Program Hotline shown in your letter immediately, with the listed documents on hand. The page prints no number of days. |
| CP5447 series (including 5447C) | A Form 1040-series return was filed under your SSN or ITIN, and the IRS needs you to verify your identity and the return. | Verify your identity and the return. If you can’t verify online, verify by phone, by mail or with the Document Upload Tool as your notice instructs. The page prints no number of days. |
| Letter 5747C | The IRS received a Form 1040-series return under your SSN or ITIN and needs to verify your identity and the return; you may need to visit a Taxpayer Assistance Center. | Act immediately. If you didn’t file, call the Taxpayer Protection Program hotline on your letter. If you did file, call the Taxpayer Assistance Center number on your letter to schedule an in-person appointment. The page prints no number of days. |
| Letter 6419 | Advance Child Tax Credit Reconciliation: the total of 2021 advance CTC payments and the number of qualifying children used to calculate them. | No response is requested. Families who received advance payments must file a 2021 return and compare the payments received with the CTC they can claim. Keep the letter with your tax records. |
| Letter 6475 | Economic Impact Payment (EIP) 3 End of Year: the total third Economic Impact Payment and any plus-up payments received for tax year 2021. | No response is requested. The letter helps determine whether you are eligible to claim the Recovery Rebate Credit on your 2021 return. |
| LT16 notice | The IRS is trying to collect unpaid taxes and/or its files show you are missing tax returns. | Read the notice and follow its instructions. File any missing returns, pay the balance, or pay what you can and set up an installment agreement. The page prints no number of days. |
| Letter 2800C | The IRS believes your employee may have filed an incorrect Form W-4, Employee’s Withholding Certificate. | Begin withholding income tax from the employee’s wages at the rates in the letter, effective 60 days from the date of the letter. Contact details are on the IRS page and the letter. |
| LT11 notice | The IRS hasn’t received your payment for overdue taxes and intends to seize your property or rights to property. You must contact the IRS immediately. | Contact the IRS immediately. Pay the unpaid balance, pay what you can, or request an installment agreement. To appeal the proposed levy, follow the instructions on the letter. The IRS page prints no number of days. |
| LT38 notice | An update on your outstanding balance because some collection notices were suspended during the pandemic and normal operations are resuming. It isn’t an audit. | Read the notice and follow its instructions. File any missing returns and pay the unpaid balance; if you can’t pay in full, see the page’s options. The page prints no number of days. |
| LT39 notice | A written reminder, required by law, about your overdue balance and any missing returns. | Pay the balance due on or before the due date on the notice. File any missing returns. If you’ve already paid, call the number on the notice. |
| Letter 2531 | Information reported on your tax return doesn’t match information reported to the IRS by third parties. The response form named on the page is for business (BMF) income tax returns. | Complete and return response Form 15114 by the date shown on the letter, saying whether you agree or disagree. If you disagree, attach a signed statement explaining each item. |
| Letter 4310C | Someone may have attempted to impersonate you using your name and Social Security number; the IRS says it resolved the issue through processing safeguards and flagged your account. | If you already filed the return for the year on the letter, submit nothing. If you haven’t, file a paper return by mail to the Submission Processing Campus for your state. Follow the letter’s instructions. |
The letter or notice number is printed on the document itself. Use it exactly as printed; the table follows the IRS page for each number. Where a response time is not printed on the IRS page, the table says so and the date on your own letter controls.
What the IRS page says the letter is
The page says: “We believe your employee may have filed an incorrect Form W-4, Employee’s Withholding Certificate.” Its FAQ calls this a lock-in letter stating the maximum number of withholding allowances permitted for the employee, sent when the IRS determines an employee does not have enough withholding.
What the IRS page asks the employer to do
Begin withholding income tax from the employee’s wages based on the withholding rates in the letter, effective 60 days from the date of the letter. The page’s example shows marital status “single” and withholding allowances “0000.” Once a lock-in rate takes effect, the page says an employer cannot decrease withholding unless the IRS approves it.
Revised Forms W-4 and online systems
The page says to disregard any Form W-4 that decreases withholding. The employee must send the new Form W-4 and a supporting statement to the IRS address on the lock-in letter for approval, and the IRS will notify you if it approves. Employers must also block locked-in employees from using an online Form W-4 system to decrease withholding. If the employee no longer works for you you don’t need to do anything, but if the employee returns within 12 months the page says to begin withholding at the letter’s rate. A follow-up modification letter, Letter 2808C, takes effect immediately on receipt.
How to get help
The page lists a toll-free number, 855-839-2235 (weekdays, 8 a.m. to 5 p.m.), a fax number, 855-202-8300, and the Withholding Compliance Unit mailing address on the IRS page. Confirm against your own letter before sending anything.
More IRS letter pages
Other pages in this set: Letter 12C, Letter 4464C, Letter 4800C, Letter 4883C, CP5447 series, Letter 5747C, Letter 6419, Letter 6475, LT16 notice, LT11 notice, LT38 notice, LT39 notice, Letter 2531, Letter 4310C. For the codes on an IRS account transcript, see the IRS transcript codes lookup. For how interest and penalties are worked out on a balance, see the IRS penalty and interest calculator.
Sources
- Understanding your letter 2800C: what the letter or notice is, what to do, and the help and reference items. Read November 2, 2026.
IRS page last reviewed October 31, 2026. This page restates what the IRS page says and adds nothing beyond it: no timelines, outcomes or advice that the IRS page does not state. The IRS can change a letter page at any time; the letter you received controls, including its response date and contact details.
Frequently asked questions
What is IRS Letter 2800C?
The IRS page says it tells an employer the IRS believes an employee may have filed an incorrect Form W-4, Employee’s Withholding Certificate.
When does the Letter 2800C withholding start?
The IRS page says to begin withholding at the rates in the letter, effective 60 days from the date of the letter.
Can I lower withholding after a lock-in?
The IRS page says that once a lock-in rate takes effect, an employer cannot decrease withholding unless the IRS approves it, and to disregard any Form W-4 that decreases withholding.
What if the employee leaves?
The IRS page says that if the employee no longer works for you, you don’t need to do anything, but if they return within 12 months you should begin withholding based on the letter’s rate.
What is Letter 2808C?
The IRS page calls it a modification letter from the Withholding Compliance Program and says changes in it become effective immediately when you receive it.
Not tax or legal advice
This page summarizes IRS letter and notice pages and is not tax, legal or financial advice. It does not tell you how to respond beyond what the IRS page states. The letter you received controls. A CPA, enrolled agent or tax attorney, or the IRS number printed on your letter, can confirm what applies to you. Everything runs in your browser; nothing you enter is sent anywhere.