As of 2015, the Internal Revenue Service provides an optional state sales tax table in the Instructions for Schedule A booklet, according to the IRS. Use either the tax table or the IRS sales tax deduction calculator to determine the amount of state sales tax to deduct on Schedule A.
The optional state sales tax table is available to view online at IRS.gov, notes the IRS. Click on the Forms & Pubs link located on the top right of the home page. Select either the Current or Prior Year tab, depending on the tax year needed. Click on the blue Find All Current Forms & Pubs link for the current tax year or the Find All Prior Year Forms & Pubs for a previous tax year. Enter Schedule A instructions into the Find box, select Title from the drop down menu, and click Find.