In banking, a TIN is a Taxpayer Identification Number: the unique number the IRS uses to track your tax activity, and the number a bank is required by federal law to collect before it can open an account in your name. For most people that number is a Social Security Number. For a non-resident who isn’t eligible for an SSN, it’s an Individual Taxpayer Identification Number (ITIN). For a business, estate, or trust account, it’s an Employer Identification Number (EIN). Whichever one applies to you, the bank will ask for it at account opening and use it again every year to report the interest you earn.
Which TIN Your Bank Will Ask For
The IRS recognizes five types of taxpayer identification numbers, but only three come up in normal banking.1Internal Revenue Service. Taxpayer Identification Numbers (TIN)
- Social Security Number (SSN). Issued by the Social Security Administration to U.S. citizens and residents authorized to work. If you have one, this is what your bank expects on a personal account.
- Individual Taxpayer Identification Number (ITIN). A nine-digit number the IRS issues to individuals who need to file a U.S. tax return but aren’t eligible for an SSN, including non-resident aliens and their dependents. The Consumer Financial Protection Bureau confirms that an ITIN qualifies as an acceptable identification number for opening a checking or savings account.2Consumer Financial Protection Bureau. Can I Get a Checking Account Without a Social Security Number or Drivers License
- Employer Identification Number (EIN). Used by businesses, estates, and trusts. A business account uses the EIN rather than the owner’s personal SSN.
The two remaining types, an Adoption Taxpayer Identification Number and a Preparer Tax Identification Number, exist for narrow tax-filing situations and don’t come up when opening a bank account.3Internal Revenue Service. PTIN Requirements for Tax Return Preparers
Business, Estate, and Trust Accounts
If you’re opening a business account, the bank will generally require an EIN. Even a single-member LLC that the IRS treats as a disregarded entity (and that would otherwise use the owner’s SSN on Form W-9) will usually be asked for one at the bank, and the IRS permits you to obtain an EIN for that banking purpose even when it isn’t strictly required for taxes.4Internal Revenue Service. Single Member Limited Liability Companies
When someone dies, the estate needs its own EIN before a bank will open an estate account. An executor cannot use the deceased person’s SSN for estate banking. The same rule applies to trusts that earn income reportable on Form 1041.5Internal Revenue Service. File an Estate Tax Income Tax Return
Why Banks Require It
Two separate federal requirements sit behind the request: identity verification and income reporting.
Customer Identification Under the PATRIOT Act
Rules implementing the USA PATRIOT Act require every bank to run a written Customer Identification Program. Before opening any account, the bank must collect your name, date of birth, address, and a taxpayer identification number. For U.S. persons, that means an SSN, ITIN, or EIN. For non-U.S. persons, the bank may also accept a passport number or alien identification card number.6eCFR. 31 CFR 1020.220 – Customer Identification Program Requirements for Banks
Reporting the Interest Your Account Earns
The second reason is tax reporting. Any time a bank pays you $10 or more in interest during a calendar year, it must file Form 1099-INT with the IRS. Without a valid TIN on file, the bank can’t complete that form correctly, and your interest becomes subject to backup withholding.7Internal Revenue Service. Instructions for Forms 1099-INT and 1099-OID (01/2024)
How You Give Your TIN to the Bank
At account opening, the bank hands you IRS Form W-9 or a substitute version of it. The form asks for your name, address, and TIN. By signing, you certify two things: that the TIN you’ve provided is correct, and that you’re not currently subject to backup withholding for past underreporting of interest or dividends. If the IRS has previously notified you that you are subject to backup withholding, you must cross out that second certification before signing.8Internal Revenue Service. Form W-9 (Rev. March 2024)
The bank then verifies your name-and-number combination against IRS records. If it matches, the account opens normally and future 1099-INTs go out under your TIN without incident.
What Happens If You Don’t Have a TIN or It Doesn’t Match
If you refuse to provide a TIN, or the number you provide doesn’t verify against IRS records, the bank is required to begin backup withholding. That means 24% of any reportable payment (such as interest on your account) is sent directly to the IRS instead of to you.9Internal Revenue Service. Backup Withholding You can eventually claim that withholding as a credit on your tax return, but the money is tied up until you file.10Office of the Law Revision Counsel. 26 USC 3406 – Backup Withholding
The “B” Notice
Mismatches happen more often than most account holders realize, usually after a name change, a data entry error, or an IRS processing mistake. When the IRS spots one, it sends the bank a CP2100 or CP2100A notice listing the affected accounts.11Internal Revenue Service. Backup Withholding B Program
The bank then forwards you a “B” notice: a warning that your TIN doesn’t match and that backup withholding will start unless you fix it. On a first B notice, submitting a fresh Form W-9 with corrected information is enough. On a second B notice within three years, the bar is higher. You’ll need to provide a copy of your Social Security card, or for an EIN, an IRS Letter 147C confirming your number.11Internal Revenue Service. Backup Withholding B Program Respond the same week you receive it. People who ignore B notices or assume they’re mistakes are the ones who lose interest to withholding they didn’t need to trigger.
Keeping Your TIN Current on the Account
A TIN on file with your bank is not a one-time errand. Two ordinary events can quietly break the match the IRS runs against its records.
The first is a name change: after marriage, divorce, or a legal name change, update your name with the Social Security Administration before you update it with the bank, so the name-and-number combination the bank submits matches what the IRS sees.
The second, for ITIN holders, is expiration. Unlike SSNs and EINs, an ITIN expires automatically on December 31 of the third consecutive year in which it isn’t used on a federal tax return. Once expired, a return filed with that ITIN will still be processed, but exemptions and credits will be disallowed until you renew using Form W-7.12Internal Revenue Service. How to Renew an ITIN The ITIN itself doesn’t stop working as an identifier on your bank account, but letting it lapse creates downstream tax problems that can bleed back into your banking through mismatched 1099-INT reporting.
The simplest defense against every backup-withholding scenario is the same: make sure the name on your bank account matches your name exactly as it appears in IRS records, and act on any B notice immediately.