Question: find out how much you owe in back taxes?
Answer: Online - check using online tool.
By phone - call the IRS at 800-829-1040, Monday through Friday 7 a.m. to 7 p.m. local time.
In-person - go to the nearest IRS office.
By mail – if you're getting letters from the IRS, then there's a good chance you have tax debt.