In the 1040 Schedule A Instructions, Line 5b, does "used for business" include renting out a room of my residence?

[David Whistler]

The instructions say, "Enter on line 5b the state and local taxes you paid on real estate you own that
wasn't used for business."  I can't find a clear statement about this in any IRS publication.  My assumption has been that any taxes I claim as an expense on Schedule E must be subtracted from the full real estate tax bill and enter that difference on Line 5b of Schedule A, but I would like to know for sure that that's what I'm supposed to do.

[SundayInSalem · Accepted solution]

Righto. Do not include on Schedule A line 5b the portion of real estate tax you deducted as a letting expense.

IRS Publication 527 says:

Be sure to report only the personal portion of your real estate taxes on line 5b of Schedule A. The personal portion of real estate taxes on the dwelling unit doesn't include the rental portion you reported on line 2b of this Worksheet 5-1 or any portion that you deducted on other forms, such as Schedule C or F.

Publication 527, Residential Rental Property

[David Whistler]

Perfect.  Thank you so much for not only answering the question but also giving the information source.