If you were legally married at the end of 2020 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 $24,800 (+$1300 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.
if you and your spouse lived apart for the last 6 months of the tax year and the taxpayer paid more than half the cost of keeping up their home along with a child (your child, stepchild or foster child who could be claimed as a dependent) who lived with the taxpayer for more than 6 months, TP can use head of household filing status.
If one of you provided care in their home for a qualifying person, usually a dependent child (but there are some exceptions) then that spouse can file HOH and the other spouse files MFS. Or, both spouses file MFS.
Or, you can still file jointly if you agree to, that will usually have the lowest tax bill or largest refund, since many deductions and credits are reduced or disallowed when filing separately. But filing jointly depends on why you are living apart, and how well you get along despite that.