No one can see your tax return. We do not know any of the amounts you are entering. If your spouse is self-employed he has to pay self-employment tax for Social Security and Medicare as well as ordinary income tax, so the amount you had withheld from your W-2 wages might not be enough to "cover or cancel out" the tax owed.
And....you mention entering things as if you were filing as Single---- which is not the same as filing married filing separately. Forget any results you get for a "single" filing status, since that does not apply to you. Your choices are to file married filing jointly or married filing separately.
It is not easy to compare MFJ to MFS using online TT but you can do it. Since you only get one return for each account and user ID, you have to use 3 accounts and user ID’s—one for MFJ and two for each of the MFS returns. Compare, choose, and file—and pay—accordingly.
It is much easier to do this comparison using the desktop version of TT installed from a CD or downloaded to your own computer. You pay once for the software and you can prepare multiple returns easily, and it has a “what if” feature that allows comparisons.
Perhaps it would be a good idea for your spouse to start making estimated quarterly tax payments for his self-employment income.
https://ttlc.intuit.com/community/self-employed/help/what-is-the-self-employment-tax/00/25922
https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/enter-self-empl...
If you live in a state with a state income tax, you might need to make estimated payments to your state.
https://turbotax.intuit.com/tax-tips/small-business-taxes/the-home-office-deduction/L1RZyYxzv
https://turbotax.intuit.com/tax-tools/calculators/self-employed/
https://ttlc.intuit.com/community/business-taxes/discussion/self-employed-don-t-miss-these-tax-moves...
https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/enter-schedule-...
https://ttlc.intuit.com/turbotax-support/en-us/help-article/payroll-additions-deductions/qualify-qua...
https://ttlc.intuit.com/turbotax-support/en-us/help-article/self-employment-taxes/self-employed-expe...
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
