As a detective, I examined the crossword clue ‘Tax ID’ carefully, trying to think of any government-related identification number that could fit the bill. My initial thought was the Individual Taxpayer Identification Number (ITIN), but it didn’t fit the space given. Then, with a flash of insight, I remembered the Social Security Number (SSN). It is a nine-digit number issued to citizens, permanent residents, and temporary residents in the United States for various purposes, including tax purposes. It’s commonly used as a unique identification number for tax identification and reporting purposes, so it perfectly fits the ‘Tax ID’ clue. With that in mind, I confidently filled in ‘SSN’ in the crossword puzzle and moved on to the next.