I amended my 2015 return to add only Social Security Benefits. How could I go from a $3000 reund to $7000 due? Total SS benefits added to income are $44500

[SweetieJean]

Did you already receive the $3000 refund?  

0-85% of your Social Security benefits are taxable, depending upon your other income. And any increase in income can also lower certain deductions and credits.

44,500 x .85 = 37,825 which is the maximum added to your taxable income. 

[SweetieJean]

Reminder: TurboTax Online is not available after midnight (tonight)-Nov 15th, 2016

[Critter]

The increased income would have also effected credits & deductions.   

If you had already filed the return then you should not have gotten the $3K refund you should have owed $4K  so you have to pay back the $3K plus the $4K that you should have owed if that SS income was entered on the original retrurn.

[SweetieJean]

Right, and $7,000 divided by 37,825 is 18%.