filing jointly, line15 shows a taxable inc of $418. Work freelance and has $537 self-employment tax. I expect to pay 537 + (10% of $418) = $578 turbo shows 537 only?

[jivepar]

It seemed the $418 was not taxed at all.

[MayaD]

Did you receive any tax credit?

Check you 1040 form, for example, Child tax credit or credit for other dependents from Schedule 8812 will show on form 1040 line 19. 

 A tax credit is a dollar-for-dollar amount you claim on your tax return to reduce the income tax you owe.

Tax credits for individuals

To preview your 1040 in TurboTax online:

1. From the left rail menu in TurboTax Online, select Tax Tools (You may have to scroll down on the left rail menu.)
2. Select Tax Tools. On the drop-down select Tools 
3. On the pop-up menu titled “Tools Center”, select View Tax Summary 
4. On the left sidebar, select Preview my 1040 

[jivepar]

No Credit at all. Lines 16 to 22 are zeroes or blanks. Line 23 shows the amount of $537 which represent only tax on self employment income.

[dmertz]

Or perhaps you have at least $418 of long-term capital gains and the $418 of taxable income is being taxed at 0%.