Calculating the Allowable Portion

Based on each taxpayer's situation, you can determine the amount of the standard deduction using one of the following:

• Standard deduction amount for the appropriate filing status:
  • Form 1040, line 12
• Standard Deduction Chart for People Age 65 or Older or Blind (Form 1040SR)

Then, you must calculate the allowable portion by using the following formula:

= Gross income subject to U.S. tax divided by
Gross income from all sources (including excluded P.R. source income)
multiplied by Standard Deduction

or
Using standard deduction worksheet in Publication 1321