Well---when you file MFS your standard deduction is much lower, so more of your income is taxable.
Your standard deduction makes some of your income "tax free"----When you file a joint return, the standard deduction for a married couple is $27,700. When you file MFS, your standard deduction is $13,850 so----you are being taxed on more of your income. And you say almost all of the income was your income.
When you file MFS you lose education credits--so if you have student loan interest you cannot deduct it.
When you file MFS you lose child-related credits like the childcare credit, earned income credit and have less income on which to base the child tax credit.
If you itemized deductions you have a lower amount for SALT---state and local taxes---it is capped at $5K instead of the $10K for a joint return.
Those are some of the reasons your tax due would have increased. It is interesting that your spouse would want to file MFS. If she has no income, then she has nothing to gain by filing MFS. She will not get any child-related credits even if she has the children--since the child-related credits are based on income earned from working, and she is disqualified automatically for some by filing MFS.
Or...are you in a community property state? That makes it even more complicated.
Community property states: AZ, CA, ID, LA, NV, NM, TX, WA, WI
More information:
If you were legally married at the end of 2023 your filing choices are married filing jointly or married filing separately.
Married Filing Jointly is usually better, even if one spouse had little or no income. When you file a joint return, you and your spouse will get the married filing jointly standard deduction of $27,700 (+$1500 for each spouse 65 or older) You are eligible for more credits including education credits, earned income credit, child and dependent care credit, and a larger income limit to receive the child tax credit.
If you choose to file married filing separately, both spouses have to file the same way—either you both itemize or you both use standard deduction. Your tax rate will be higher than on a joint return.
Some of the special rules for filing separately include: you cannot get earned income credit, education credits, adoption credits, or deductions for student loan interest. A higher percent of your Social Security benefits may be taxable. Your limit for SALT (state and local taxes and sales tax) will be only $5000 per spouse. In many cases you will not be able to take the child and dependent care credit. The amount you can contribute to a retirement account will be affected. If you live in a community property state, you will be required to provide additional information regarding your spouse’s income. ( Community property states: AZ, CA, ID, LA, NV, NM, TX, WA, WI)
If you are using online TurboTax to prepare your returns, you will need to prepare two separate returns and pay twice since with online, you get one return per fee.
https://ttlc.intuit.com/questions/1894449-married-filing-jointly-vs-married-filing-separately
https://ttlc.intuit.com/questions/1901162-married-filing-separately-in-community-property-states
https://ttlc.intuit.com/questions/1894449-is-it-better-for-a-married-couple-to-file-jointly-or-separ...
**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.**
