Real or Fake TIN?

A stack of taxpayer ID cards and a swipe: valid format right, impossible left, then name the kind of TIN and read IRS TIN matching result codes 0 to 8. Streaks charge a combo meter, and every miss lights up the exact digits that gave it away.

You will learn the SSN, ITIN and EIN format rules, ATINs and IRSNs, and what each TIN matching code meansPrivacy runs in your browser; scores stay on your device

How to play

Press Start swiping. Round 1 (10 cards): each card claims to be an SSN, ITIN or EIN. Swipe right, tap Valid format or press → if the number could exist; swipe left, tap Impossible or press ← if it can never be issued.
Round 2 (8 cards): name the kind of TIN: SSN, ITIN, ATIN, EIN or IRSN. Tap or press 1 to 5.
Round 3 (7 cards): an IRS TIN matching result comes back. Say what the code means, what kind of result it is, what you do next, or whether a filed pair reaches a CP2100. Tap or press 1 to 4.
Beat the timer bar: faster answers score more, and every 3 right in a row add to your combo, up to x4. A miss lights up the digits that gave it away; press Next or Enter to go on.

Every number in the game is made up. A "valid format" card only means the digits follow the rules, not that the number belongs to anyone.

The real rules behind the game

Real or Fake TIN? drills the two checks a payer can run on a taxpayer identification number: a format check you can do yourself, and IRS TIN matching, which only the IRS can answer. Round 1 uses exactly the rules of the site's TIN format checker; round 2 follows the table on What is a TIN? and the ITIN guide; round 3 uses the TIN Matching result code decoder.

What makes a number impossible

Every TIN is nine digits. Letters, or eight digits because a spreadsheet dropped a leading zero, come back from TIN matching as code 1. An SSN can't have area (first three digits) 000, 666 or 900 to 999, group (middle two) 00 or serial (last four) 0000; since 2011 the Social Security Administration assigns numbers randomly, so nothing else about the area means anything. An ITIN begins with 9 and its fourth and fifth digits fall in 50 to 65, 70 to 88, 90 to 92 or 94 to 99. An EIN starts with a two digit prefix from a fixed IRS list; prefixes such as 00, 07, 08, 09, 17, 18, 19, 28, 29, 49, 69, 70, 78, 79, 89, 96 and 97 have never been issued. Placeholders fail even when they pass the structure rules: repeated digits, 123456789, the Woolworth number 078-05-1120 and the SSA advertising range 987-65-4320 to 4329.

Telling the kinds apart

By convention an SSN or ITIN is written ###-##-#### and an EIN ##-#######. A 9 up front means the number is not an SSN, and the middle pair says what it is: an ITIN range, 93 for an ATIN (an adoption TIN for a child, not a payee's TIN), 89 reserved, or an IRS campus code (01 to 10, 17 to 19, 28, 29, 37 to 39, 49, 66) for an IRSN, an internal IRS number that is not a valid TIN. The ITINs on W-9s and 1099s guide quotes the IRS manual on each range.

The nine result codes

TIN matching checks a name and TIN pair against IRS records and answers with one digit. 0 is a match; 6, 7 and 8 are matches on SSN, EIN or both, and come back only when you send the TIN type as unknown. 2 (not currently issued) and 3 (name and TIN don't match) are payee problems: get a corrected W-9 and match again before you file, or expect the pair on the next CP2100. 1 (missing or not nine digits), 4 (invalid request) and 5 (duplicate request) are about your own data or file: fix it and resubmit. If a return goes out with a code 1 TIN, it comes back on the CP2100 as a missing TIN: backup withhold and make the annual solicitations, but send no B-Notice. Never try several spellings of a name against one TIN; it locks the TIN Matching account for 96 hours. The TIN matching guide and When a TIN does not match IRS records cover the causes.

What the game simplifies

Passing a format check means the number could exist, not that it is issued or belongs to the name on the W-9. Nine bare digits can be a possible SSN and a possible EIN at once, which is why TIN matching asks for a TIN type; round 2 uses the dash pattern as the clue. Round 3 shows one result per card and a short version of each next step; the decoder lists the full steps and which codes reach a CP2100.

Sources

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