At the top of Form 4797, there is a section for "Identifying number", but I was unable to find anything in the documentation about it.

Is this just my SSN, or is it some other identifying number? Is this documented somewhere in the instructions?

1 Answer 1


I believe so. Looking at my own return, other forms specifically ask for social security numbers in that box which is (to the best of my knowledge) only used to help associate loose forms with your return if/when they are separated.

Other forms have (at least in the past) also said something like "SSN or taxpayer identification number" for the corresponding box.

  • TIN, taxpayer ID number, is either SSN or a company's equivalent identification, depending on who/what is filing the tax return. I'm not familiar with that particular form, but this seems likely. What does the text of the form's instructions say?
    – keshlam
    Commented Apr 16, 2023 at 18:19
  • I haven't read the entire document word-for-word, but it doesn't appear to have anything to say about the who-is-filing information common to all tax forms.
    – chepner
    Commented Apr 16, 2023 at 18:38
  • 4947 is sale of business property. If your business is a pass-through company and you just file its finances as part of your own taxes, I'd assume SSN; if the company is its own taxable entity, I'd assume this would appear as part of its tax forms and you'd use its TIN. That is, these are the "identifying numbers" that go with the "names shown on the return" to their left. But don't take my word for it.
    – keshlam
    Commented Apr 16, 2023 at 20:02

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