What’s the irs fax number

[DoninGA]

There are no IRS published fax telephone numbers.  Only if you receive a notice or letter from the IRS requesting information that can be faxed would a fax number be available to you.

What exactly are you trying to fax?

[Texas Roger]

You can't fax something to the IRS unless they sent you a specific request for information and provided a fax number for you to send it to them. If that is what happened, no one else has the fax number that they provided to you.