Taxpayer ID forms fall into two groups: forms that apply for a number and forms that certify a number you already have. Which one you need depends on your situation. Form SS-5 applies for a Social Security number through the Social Security Administration. Form W-7 applies for an Individual Taxpayer Identification Number (ITIN) when you have a US filing requirement but can’t get an SSN. Form SS-4 applies for an Employer Identification Number (EIN) for a business. Once you have a number, Form W-9 certifies it to a US payer, and the W-8 series does the same for foreign payees. Two narrower forms exist for special cases: Form W-7A for a pending US adoption, and the PTIN application for paid tax return preparers.
Which Form Matches Your Situation
Use Form SS-5 if you’re a US citizen, permanent resident, or work-authorized noncitizen applying for a Social Security card. Use Form W-7 if you have a US tax filing obligation but aren’t eligible for an SSN. Use Form SS-4 if you’re forming a business entity, hiring employees, or otherwise need an EIN. Use Form W-9 when a US bank, client, or broker asks you to certify your TIN so they can report payments to you. Use a form in the W-8 series if you’re a foreign person receiving US-source income and need to establish foreign status or claim a treaty rate.
Two boundary points worth flagging before you pick a form. Form W-7A is only for a child placed in your home for legal adoption when you can’t get the child’s SSN in time to file; if the child isn’t a US citizen or resident, you’d file a W-7 for an ITIN instead.1Internal Revenue Service. About Form W-7 A, Application for Taxpayer Identification Number for Pending U.S. Adoptions The Preparer Taxpayer Identification Number (PTIN) is only for people who prepare federal returns for compensation, not for taxpayers themselves.2Internal Revenue Service. Taxpayer Identification Numbers (TIN)
Form SS-5: Social Security Number
Form SS-5 is filed with the Social Security Administration, not the IRS. For an original card, you’ll submit at least two documents proving age, identity, and US citizenship. The SSA accepts only original documents or copies certified by the agency that issued them. Notarized photocopies are not accepted.3Social Security Administration. Application for a Social Security Card (Form SS-5)
A birth certificate is the standard document for proof of age. The SSA also accepts a US hospital birth record created at the time of birth, a religious record from before age five, or a US passport. For identity, the preferred documents are a US driver’s license, state-issued ID card, or US passport. A birth certificate cannot be used to prove identity; it only satisfies the age requirement. For citizenship, a birth certificate or US passport is standard, and a Certificate of Naturalization or Consular Report of Birth also qualifies.3Social Security Administration. Application for a Social Security Card (Form SS-5)
Form W-7: Individual Taxpayer Identification Number
If you have a US tax filing requirement but can’t get an SSN, Form W-7 is your route to an ITIN. Most first-time applicants must submit a completed federal income tax return along with the application. A few exceptions exist, such as certain third-party withholding situations and treaty benefit claims, but most applicants file the return with the W-7.4Internal Revenue Service. About Form W-7, Application for IRS Individual Taxpayer Identification Number
An ITIN is strictly for federal tax purposes. It does not authorize employment, and it doesn’t qualify you for Social Security benefits or the earned income credit.5Internal Revenue Service. Topic No. 857, Individual Taxpayer Identification Number (ITIN)
Documents to Include
You’ll need original documents or certified copies from the issuing agency to prove both identity and foreign status. A valid passport is the only single document that proves both at once. Without a passport, submit one document for identity and one for foreign status.6Internal Revenue Service. Instructions for Form W-7
Dependent applications have stricter rules. A civil birth certificate is required, plus proof of US residency. A passport without a US date-of-entry stamp does not stand alone for a dependent; additional documents must show the dependent actually lives in the US. The name and date of birth on the W-7 must match the supporting documents exactly, because even small discrepancies cause rejection.7Internal Revenue Service. Instructions for Form W-7
How to Submit
Three routes exist. You can mail the form, the tax return, and your original documents to the IRS ITIN Operations office. The IRS returns the originals after processing, but you’re without them during that window.
You can also use a Certifying Acceptance Agent (CAA), an IRS-authorized professional who verifies your original documents and sends only certified copies to the IRS. This lets you keep your originals. CAA fees typically run from around $50 to several hundred dollars depending on complexity and location.
The third option is an in-person appointment at a designated IRS Taxpayer Assistance Center, where you present documents directly. Appointments can be difficult to schedule during filing season.
How Long It Takes
A complete W-7 generally takes about seven weeks to process. During tax season (January 15 through April 30) or when mailed from overseas, expect nine to eleven weeks.8Internal Revenue Service. How to Apply for an ITIN
Renewing an Expired ITIN
An ITIN not used on a federal tax return at least once in the past three years automatically expires. ITINs with middle digits 83 through 87 have also expired under rolling schedules tied to an IRS modernization effort. Renewal uses the same Form W-7 as a new application.9Internal Revenue Service. How to Renew an ITIN
One useful exception: if your ITIN appears only on information returns like a Form 1099, you don’t need to renew it. Expired ITINs can still be used on information returns. Renewal is only required when the ITIN will appear on a federal tax return. Spouses and dependents renewing to claim an allowable tax benefit must be listed on an attached tax return with the relevant schedule or form.9Internal Revenue Service. How to Renew an ITIN
Form SS-4: Employer Identification Number
Form SS-4 applies for an EIN. The online application issues the number immediately, so a business can get its EIN the same day it applies.10Internal Revenue Service. Get an Employer Identification Number
EINs are for business entities such as corporations, partnerships, and LLCs taxed as corporations or partnerships. A sole proprietor also needs one to hire employees or run a qualified retirement plan.11Internal Revenue Service. About Form SS-4, Application for Employer Identification Number
Information You’ll Need
The application asks you to name a “responsible party”: the individual who ultimately owns or controls the entity and can direct its funds. For most entities this must be an actual person, not another business, and that person must have a valid SSN or ITIN. If the responsible party is foreign and ineligible for either, you can enter “foreign” on the application, but the online system won’t work for you.12Internal Revenue Service. Instructions for Form SS-4
You’ll also enter the entity’s legal name, any trade name, the type of entity, and your reason for applying (starting a new business, hiring employees, opening a business bank account, changing how the business is organized). The online system times out after 15 minutes of inactivity, so gather everything before starting. A wrong responsible-party TIN is one of the most common reasons applications get rejected.
Filing Methods
Any entity whose principal place of business is in the US or a US territory can apply online for free and receive the EIN on the spot. Entities without a US location apply by fax, mail, or phone. Fax takes about four business days. Mail takes four to five weeks. International applicants without a US-based responsible party can call the IRS and get the EIN during the call.13Internal Revenue Service. Employer Identification Number
When a New EIN Is Required
A change in business structure or ownership often means a new EIN; the old one doesn’t carry forward. A sole proprietor who incorporates must get a new EIN. A corporation that merges to create a new entity needs one. A partnership that dissolves and re-forms needs a new number. The general rule: if the legal identity of the entity changes, so does the EIN.14Internal Revenue Service. When to Get a New EIN
Form W-9: Certifying Your TIN to a US Payer
Once you have a TIN, banks, clients, brokers, and other payers will ask you to certify it before they report payments to you on a Form 1099. Form W-9 is that certification. It goes to the payer, not the IRS.
By signing a W-9, you certify under penalty of perjury that the TIN is correct, that you are not subject to backup withholding (or you cross out that certification if you are), that you are a US person, and that any FATCA exemption code you entered is correct.15Internal Revenue Service. Form W-9, Request for Taxpayer Identification Number and Certification
If you don’t give the payer a correct TIN, or refuse to submit one at all, the payer is generally required to withhold 24% of certain payments and send it to the IRS as backup withholding. You’ll get credit for the withheld amount when you file your return, but the money is out of your hands until then.16Internal Revenue Service. Topic No. 307, Backup Withholding
Form W-8 Series: Certifying Foreign Status
Foreign individuals and entities use the W-8 series to establish foreign status and, where applicable, claim a reduced withholding rate. The default withholding rate on most US-source income paid to a foreign person is 30%. A tax treaty between the US and the payee’s country of residence can reduce or eliminate that rate.17Internal Revenue Service. NRA Withholding
The most commonly used form is the W-8BEN, for a nonresident alien individual to establish foreign status and claim treaty benefits on income such as dividends or royalties. Foreign entities use the W-8BEN-E. Income effectively connected with a US trade or business is reported on Form W-8ECI.
A W-8BEN is generally valid from the date signed through the end of the third calendar year after signing. A form signed at any point in 2026, for example, expires on December 31, 2029. If any information becomes incorrect before that date, submit a new form within 30 days.18Internal Revenue Service. Instructions for Form W-8BEN