I only have social security income and an ira distribution of $1500 so gross income is $1500 do I have to file federal income tax?

If your only source of income, other than your social security, is a $1500 retirement distribution, then your social security is not taxable. Your "combined income" would have to be over $25,000 on a single return or $32,000 on a joint return.  The calculation of the income is your Adjusted Gross Income (excluding Social Security) plus one half of your social security benefits, plus any tax free income.  So, in your case $1500 + 1/2 of your social security = your "combined income".

If the social security is not taxable, you do not have to file. 

Information on the taxable social security calculation can be found at the link below:

https://www.ssa.gov/planners/taxes.html 

Please see the link below for information on who has to file a return.

https://ttlc.intuit.com/replies/3302274