I don't understand why my SS income is partly taxable. My wage income is $7,300. Social security wages is $14,736. I am filing married filing seperately.

The basic formula to determine whether your Social Security benefits are taxable includes half of your Social Security income plus all other sources of income, including any tax-exempt interest. Once this total exceeds the base amount for your filing status, a portion of your Social Security income becomes taxable. The three base amounts are:

• $25,000 for single, Head of Household, and qualifying surviving spouse with a dependent child or married individuals filing separately who didn't live with their spouse at any time during the year
• $32,000 for married couples filing jointly
• $0 for married persons filing separately who lived together at any time during the year

 Generally, up to 50% of your benefits will be taxable. However, up to 85% of your benefits can be taxable if either of the following situations applies to you.

 • The total of one-half of your benefits and all your other income is more than $34,000 ($44,000 if you are married filing jointly).

 • You are married filing separately and lived with your spouse at any time during 2022. 

For more information: IRS Pub. 915

It is simply a rule that if you file MFS, 85% of your SS benefits are automatically taxable.  There are a number of tax disadvantages to MFS, this is one of them.