There is no single “tax registration certificate” in the United States, so proof of income tax registration means producing the IRS document that matches your identifier: an EIN confirmation letter (CP 575) or Letter 147C for a business, a CP 565 assignment notice for an ITIN holder, or a Social Security card for an individual with an SSN. In many situations you’ll also be asked for a tax transcript that shows the IRS actually has you on file.
Federal law requires anyone filing a return, or anyone about whom a return is filed, to include an identifying number.1Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers That number is your registration. The paper that proves you hold it depends on which type you have.
Which Number You Hold, and What Proves It
Three taxpayer identification numbers cover almost everyone in the U.S. tax system.
- The Social Security Number is issued by the Social Security Administration to U.S. citizens and authorized residents. Your Social Security card, paired with a government-issued photo ID, is the proof most employers and banks will accept.
- The Employer Identification Number is a nine-digit number the IRS assigns to businesses, nonprofits, estates, and trusts. Any entity that hires workers or operates as a partnership or corporation needs one.
- The Individual Taxpayer Identification Number is a tax-processing number for people who must file a federal return but don’t qualify for an SSN, including certain nonresident and resident aliens and their dependents.
EIN: The CP 575 Letter and Its Replacement
When the IRS approves a new Employer Identification Number, it issues Notice CP 575 as confirmation. The letter shows the EIN, the business name, the filing address, and which federal tax forms the entity must file. Banks, payroll providers, and government agencies routinely accept this notice as proof that a business is registered with the IRS.2Internal Revenue Service. Get an Employer Identification Number
The CP 575 is issued only once. If you’ve lost yours or never received it, call the IRS Business and Specialty Tax Line and request Letter 147C. The agent can fax it to you the same day or mail it to the address on file, and 147C is treated as an acceptable substitute for the original confirmation.3Internal Revenue Service. Employer Identification Number
ITIN: Notice CP 565
The IRS sends Notice CP 565 to confirm that an ITIN has been assigned or renewed. The notice lists your ITIN, full name, and date of birth. It also reminds you that the ITIN must be used on at least one federal return within a three-year period or it will expire, and that it does not change your immigration status or authorize employment.4Internal Revenue Service. CP 565 Notice
SSN: The Card Itself
For individuals, the Social Security card is the proof. Presented alongside a government-issued photo ID, it satisfies almost every employer and financial institution that asks whether you have a valid tax identification number. A separate IRS document is rarely required.
When You Need to Prove You’ve Actually Filed
Sometimes the identifier alone isn’t enough. Lenders, schools, and government programs want to see that you’re in the IRS system and that returns have been processed. Tax transcripts do that job, and the IRS provides them at no charge.5Internal Revenue Service. Transcript Types for Individuals and Ways to Order Them Four are commonly requested:
- The tax return transcript shows most line items from your original Form 1040 as filed. It’s available for the current year and three prior years, and mortgage lenders commonly accept it.
- The tax account transcript displays filing status, taxable income, payment types, and any changes made after filing. It’s available for up to nine prior years through your online account.
- The wage and income transcript shows data from W-2s, 1099s, and other information returns filed with the IRS. It’s available for the current year and nine prior years.
- The verification of non-filing letter confirms that the IRS has no record of a processed return for a specific year. It’s available after June 15 for the current tax year, or anytime for the prior three years, and is useful for dependents applying for financial aid who need to prove they’re in the system but weren’t required to file.6Internal Revenue Service. Get Your Tax Records and Transcripts
How to Get These Documents
Through Your IRS Online Account
The fastest route to transcripts and verification letters is the IRS Individual Online Account, where you can view, print, or download them immediately as PDFs. To create an account you need a personal email address, a government-issued photo ID, and your SSN or ITIN. The IRS uses ID.me to verify your identity, which involves uploading your photo ID and either taking a selfie or completing a video call.7Internal Revenue Service. Creating an Account for IRS.gov
Business owners can access a separate Business Tax Account through the same ID.me verification. Tax professionals who need records for clients can use e-Services after filing Form 2848 (Power of Attorney) or Form 8821 (Tax Information Authorization), both of which can be submitted online.8Internal Revenue Service. About Form 2848, Power of Attorney and Declaration of Representative
By Phone or Mail
You can request transcripts by calling 800-908-9946 or by mailing Form 4506-T. There is no fee, but delivery takes five to ten business days.5Internal Revenue Service. Transcript Types for Individuals and Ways to Order Them If you need an actual photocopy of a previously filed return rather than a transcript, use Form 4506, which carries a $30 fee per return.9Internal Revenue Service. Form 4506 – Request for Copy of Tax Return
For EIN verification, call the IRS Business and Specialty Tax Line and ask for Letter 147C.3Internal Revenue Service. Employer Identification Number
Form W-9: The Proof You Hand to Payers
In everyday practice, the document you’ll complete most often to prove your tax registration is Form W-9, Request for Taxpayer Identification Number and Certification. Any business that will pay you and must file an information return with the IRS will ask you to fill one out. By signing, you certify that your TIN is correct, that you’re not subject to backup withholding, and that you’re a U.S. person for withholding purposes.10Internal Revenue Service. Form W-9 – Request for Taxpayer Identification Number and Certification
A completed W-9 stays with the payer and is not filed with the IRS. Refuse to provide one, or give an incorrect TIN, and the payer must withhold 24% of your payments as backup withholding and remit it to the IRS.11Internal Revenue Service. Backup Withholding
Proving U.S. Tax Residency Abroad: Form 6166
If a foreign country or a treaty partner needs proof that you are a U.S. resident for tax purposes, the transcripts and CP notices above will not do the job. You need Form 6166, a letter on U.S. Department of Treasury stationery certifying U.S. residency for federal income tax purposes. Many treaty partners require it before granting reduced withholding on dividends, royalties, or other income, and some countries accept it for VAT exemption.12Internal Revenue Service. Form 6166 – Certification of U.S. Tax Residency
To get Form 6166 you file Form 8802. As of September 2025, individual applicants can submit Form 8802 digitally; business entities must still file on paper. The user fee is $85 for individuals and $185 for non-individual applicants, regardless of how many countries or tax years the certification covers.13Internal Revenue Service. Instructions for Form 8802 One boundary worth knowing: Form 6166 cannot be used to prove you paid U.S. taxes for purposes of claiming a foreign tax credit. Its scope is limited to residency.14Internal Revenue Service. About Form 8802, Application for U.S. Residency Certification
Fixing Name and Address Mismatches
Your proof only works when the information on IRS records matches what you present. A name or address mismatch will cause rejected transcript requests, delayed refunds, and failed identity verification.
Individuals notify the IRS of a new home mailing address using Form 8822.15Internal Revenue Service. About Form 8822, Change of Address Businesses use Form 8822-B, which also covers changes to the responsible party associated with an EIN, and should file within 60 days of a change. Both forms are paper-only and typically take four to six weeks to process.
If a payer receives an IRS notice that the name and TIN you provided don’t match, you’ll need to correct the discrepancy to stop backup withholding. The IRS matches the first four characters of your last name (for individuals) or entity name (for businesses) against the TIN on file, so even a minor variation, like a maiden name on one form and a married name on another, will trigger a mismatch.16Internal Revenue Service. Reasonable Cause Regulations and Requirements for Missing and Incorrect Name/TINs
For individuals who changed their name through marriage, divorce, or court order, the Social Security Administration must update the name first. The IRS pulls name data from SSA records, so updating only one agency leaves the mismatch in place. Businesses that change their legal name generally do not need a new EIN unless the entity’s legal structure also changed; filing the next return under the new name is usually sufficient to update IRS records.
Keep the original CP 575, CP 565, or Social Security card in a place you can find it. Replacing any of them is possible, but each replacement adds a wait, and the document you already have is the quickest proof you can produce when someone asks.