| Clue | Source | Date |
|---|---|---|
| SSN, often | Wall Street Journal | 23 Aug 2023 |
| IRS number | Newsday | 22 Nov 2020 |
| No. on an IRS form | LA Times Daily | 28 Aug 2018 |
| No. on an IRS form | The Washington Post | 28 Aug 2018 |
| No. on an IRS form | ||
| S.S.N., e.g | New York Times | 26 Jul 2017 |
| S.S.N., e.g. | ||
| IRS number | ||
| Identifier for the 21 Down | ||
| SSN, for example |