Yes — if you earn money through affiliate marketing, you need a tax ID number for affiliate marketing income, because every network that pays you has to collect one before it sends a dollar. For most solo affiliate marketers in the United States, that tax ID is simply your Social Security Number. If you’ve formed a partnership, a corporation, or a multi-member LLC, you’re required to get an Employer Identification Number instead. And even when the law lets you use your SSN, there are practical reasons to get an EIN anyway.
Which Tax ID Fits Your Business Structure
The IRS uses a nine-digit Taxpayer Identification Number to track your tax activity, and the type you need depends on how your business is organized.1Internal Revenue Service. Taxpayer Identification Numbers
Sole Proprietor
If you haven’t registered a business entity with your state and you’re running affiliate links under your own name, you’re a sole proprietor by default. Your SSN is your business tax ID. You give it to every affiliate network you join, and you report the income on Schedule C of your personal return.2Internal Revenue Service. Instructions for Schedule C (Form 1040)
A sole proprietor is only required to get an EIN if they hire employees or need to file excise tax returns.3Internal Revenue Service. Employer Identification Number Everything else is optional.
Single-Member LLC
A single-member LLC is registered at the state level but treated as a “disregarded entity” by the IRS for income tax purposes. The IRS looks through the LLC and treats the income as yours, reported on Schedule C the same way a sole proprietor would.4Internal Revenue Service. Single Member Limited Liability Companies
For income tax reporting, a single-member LLC can use the owner’s SSN or ITIN. The IRS requires the LLC to get its own EIN only if it has employees, files excise tax returns, or elects to be taxed as a corporation.5Internal Revenue Service. Entities If you want an EIN anyway for banking or privacy, the IRS will issue one.4Internal Revenue Service. Single Member Limited Liability Companies
Partnerships, Multi-Member LLCs, and Corporations
Once more than one person owns the business, an EIN is mandatory. Multi-member LLCs, partnerships, S corporations, and C corporations all must have one.3Internal Revenue Service. Employer Identification Number A multi-member LLC defaults to partnership classification for federal tax purposes unless it files Form 8832 to elect corporate treatment.6Internal Revenue Service. LLC Filing as a Corporation or Partnership If you run affiliate links with a partner, even informally, you need an EIN regardless of how small the operation is.
If You’re Not Eligible for an SSN
Nonresident and resident aliens who aren’t eligible for a Social Security Number use an Individual Taxpayer Identification Number (ITIN) in its place for tax reporting. An ITIN doesn’t authorize employment in the U.S., but it works the same way as an SSN on a W-9.7Internal Revenue Service. Individual Taxpayer Identification Number
Why Many Solo Affiliates Get an EIN Anyway
Nothing stops a sole proprietor or single-member LLC owner from using their SSN. The question is whether you want to hand that number to a dozen different companies. Each W-9 you submit sits in another company’s records, and every added copy is another chance for your SSN to leak in a breach.
An EIN eliminates that exposure. It’s free to get, it’s issued immediately through the IRS online tool, and it slots into any field that would otherwise ask for your SSN on business paperwork. Most banks also require an EIN to open a business checking account, and keeping business money separate from personal money makes tax time dramatically easier.
The W-9, the 1099-NEC, and Backup Withholding
Before any affiliate network pays you, it will ask you to fill out IRS Form W-9. The form collects your legal name, business type, and TIN so the network can report what it paid you to the IRS.8Internal Revenue Service. About Form W-9
For the 2026 tax year, the reporting threshold for nonemployee compensation is $2,000. If a network pays you $2,000 or more during the calendar year, it must issue you a Form 1099-NEC.9Internal Revenue Service. 2026 Publication 1099 The previous threshold was $600, and the change applies to payments made after December 31, 2025.10Internal Revenue Service. Form 1099-NEC and Independent Contractors One copy of the 1099 goes to you, one goes to the IRS, and your TIN is what links the network’s report to your return.
If you don’t provide a valid TIN on your W-9, or if the IRS tells the network your TIN is wrong, the network must withhold 24% of your payments and send that money straight to the IRS. This is called backup withholding.11Internal Revenue Service. Topic No. 307, Backup Withholding You can recover the withheld amount when you file, but in the meantime a quarter of your earnings is locked up. Filling out the W-9 correctly from the start avoids the whole mess.
Backup withholding can also apply if the IRS has previously notified you about underreported interest or dividend income and you fail to certify on the W-9 that you’re not subject to it.11Internal Revenue Service. Topic No. 307, Backup Withholding
You Still Owe Tax Below the 1099 Threshold
This is where affiliate marketers most often get into trouble. The $2,000 threshold is a reporting requirement for the network, not a tax-free allowance for you. If you earn $1,500 from one network and $800 from another, neither one has to send you a 1099, but you still owe income tax and self-employment tax on all $2,300.
The IRS requires you to report all income on your tax return regardless of whether a 1099 shows up in the mail.12Office of the Law Revision Counsel. 26 USC 6109 – Identifying Numbers Affiliate marketers who work with many small programs can easily earn substantial income without receiving a single form. The income is still taxable, and leaving it off your return can trigger penalties and interest if the IRS matches other records against what you filed.
How to Get an EIN
Applying for an EIN is free. The IRS online application is the fastest route; if your application is approved, the EIN is issued immediately on screen.13Internal Revenue Service. Get an Employer Identification Number
To use the online tool, your principal place of business must be in the U.S. or a U.S. territory, and you need the SSN or ITIN of the responsible party who controls the entity. The application has to be completed in one sitting. It expires after 15 minutes of inactivity, and you can’t save your progress, so have your business structure, address, and responsible-party information ready before you start.13Internal Revenue Service. Get an Employer Identification Number
If you can’t use the online application, typically because your business is based outside the U.S., you can fax or mail Form SS-4. Faxed applications generally produce an EIN within four business days. Mailed applications take about four weeks. International applicants can also apply by phone.14Internal Revenue Service. Instructions for Form SS-4
Once you have the number, use it on every W-9 you fill out from that point forward. Networks you joined before getting the EIN will usually let you submit an updated W-9 to replace your SSN on file.