Healthcare tax credit/marginal rate

[The-old-version-was-easier]

Turbotax calculates a $740 tax liability on what it says is about $2300 of income. 

I had Social Security, a pension, interests, dividends and had capital losses.  The $2300 did not include the Social Security.  Including it, I would have had about $28k.

I think the $2300 was my Taxable Income (line 11b).  I'm not sure why it hasn't shown me the AGI.  That was confusing.

The tax tables say the tax on either $2300 or $28000 is bout 10%.   But 740 is either 2.5% of the larger number or 30% of the AGI.  

After digging it said I got too much of a tax credit for my Medicare.  Somehow my brain broke down here after going through all this.

Anyone care to explain this to a tax-impaired person who may have lost more brain cells than he cares to admit?

[KristinaK]

It seems there is an error while entering information. Without seeing your tax return it's hard to tell. You have two options:

1) Print or create a pdf of your entire tax return and go over each line to see if something sticks out. Doing a two-year comparison also helps. 

2) Create a diagnostic copy of your return (it's a sanitized version with no sensitive information in it), and we can take a look for you. Here is how you create the diagnostic copy token. 

For TurboTax Online:

• From the left menu, click Tax Tools
• Tools
• Share my file with agent click send
• There will be a pop-up with a token number