A sales tax ID number doesn’t have one standard look. Each state designs its own numbering system, so the ID can be a short run of digits, a long one, a hyphenated string broken into segments, or an alphanumeric code that starts with a two-letter prefix. What a sales tax ID number looks like depends entirely on which state issued it.
The Formats You’ll Actually See
Purely numeric IDs are the most common type, but the digit count varies widely from state to state. Some states issue IDs as short as seven or eight digits. Others assign eleven- or thirteen-digit strings. There’s no national convention on length.
A handful of states build dashes or hyphens into the number, splitting it into segments the way a federal EIN uses a dash after its first two digits. Others run the digits together with no punctuation at all.
Some states add a two-letter prefix that identifies the account type or the jurisdiction, which produces an alphanumeric format rather than a pure number. A few states take a different approach and incorporate part of the business’s federal EIN directly into the state sales tax number, which lets the tax agency cross-reference federal filings with state sales tax accounts. Still others assign a completely independent number that bears no resemblance to any federal identifier the business holds.
Put those variations together and you get a wide spread: a seven-digit number from one state, a hyphenated eleven-digit string from the next, and an alphanumeric code with a state prefix from a third. All three are valid sales tax IDs. None of them look like each other.
Why You Can’t Validate a Number by Looking at It
Because formats differ so much, there’s no way to glance at a sales tax ID and know whether it’s genuine based on structure alone. A nine-digit number that looks like it could be an EIN might actually be a state sales tax ID. A thirteen-digit string that looks oddly long is normal in some states and unheard of in others.
The number printed on your certificate of authority, seller’s permit, or sales tax license is the one your state uses, and its format is whatever that state’s tax agency assigns. If you need to confirm a format, the state tax agency’s website is the authoritative place to check.
Where to Find Your Number
After you register, the state issues the ID along with a certificate of authority, seller’s permit, or sales tax license. The document goes by different names in different states, but it’s the same thing: your official proof that you’re authorized to collect sales tax, and it carries the ID number on its face.
Most states legally require you to display this certificate at each location where you make taxable sales, so for brick-and-mortar businesses the number is usually posted somewhere visible on site. For online sellers, it lives in the registration confirmation and in the account dashboard of the state tax portal.
How a Sales Tax ID Differs From an EIN
People regularly confuse the two numbers, partly because they’re both tax identifiers and partly because the EIN has a format recognizable enough that it becomes the mental template for every other tax number. It isn’t.
A federal Employer Identification Number is always nine digits formatted as XX-XXXXXXX. The IRS assigns it to identify a business for federal purposes like income tax and payroll reporting.1Internal Revenue Service. Understanding Your EIN Nearly every business entity needs one, and the format never changes.
A sales tax ID is issued by a state tax agency and exists solely for collecting and remitting sales and use tax within that state. The format is set by the state, not by any federal rule. A business can hold an EIN and never need a sales tax ID if it doesn’t sell taxable goods or services. A sole proprietor making retail sales might need a sales tax ID even if they use their Social Security number instead of an EIN for federal filings.2Streamlined Sales Tax. Registration FAQ
The two numbers are also used differently. The EIN identifies the business to the federal government across every type of federal tax. The sales tax ID identifies the business to a single state tax agency for one specific purpose. Mixing them up on a form, a resale certificate, or a return causes rejections and delays.
A Note on “Resale Numbers”
You’ll sometimes hear the sales tax ID called a “resale number” or “resale permit number,” especially when a business is using it to buy inventory tax-free from a supplier. There’s no separate resale number. The ID that appears on a resale certificate is the sales tax ID itself. The certificate is a form; the number on it is the one the state issued when you registered.
Multi-State Sellers End Up With a Mismatched Set
If you sell into more than one state and are registered in each, you’ll hold a separate sales tax ID from every state where you’re registered. Each one follows that state’s own format, so your collection of IDs may look like an assortment of unrelated account numbers rather than variants of a single pattern.
The practical consequence is organizational. You need the correct number for the correct state every time you file a return, issue a resale certificate, or respond to a tax notice. A number that works in one state is meaningless in another, and the format differences mean you can’t rely on recognizing them visually. Keeping a labeled list, with the issuing state next to each number, saves time and prevents filing mistakes.
Verifying a Number You’ve Been Given
If you’re a wholesaler or supplier accepting a resale certificate from a customer, format alone won’t tell you whether the ID is real. Many state tax agencies offer free online verification tools where you can enter a number and confirm whether it’s active in that state. These tools confirm the number only within the state that runs the tool; they won’t check out-of-state IDs or federal numbers.
Running a quick verification at the point of sale costs nothing. If you accept a resale certificate with an invalid or expired sales tax ID and the transaction is later audited, you can be held responsible for the uncollected sales tax, so treating verification as routine protects the business.
The One-Line Summary
A sales tax ID looks like whatever the issuing state wants it to look like: anywhere from roughly seven to thirteen characters, numeric or alphanumeric, with or without hyphens, with or without a state prefix, sometimes built around the business’s EIN and sometimes not. The number on your state-issued certificate is the authoritative version, and the state tax agency is the only source that can confirm whether a given number is valid.