I got married on July 20, 2019. Can I file single?

Not unless you got divorced before the end of 2019.

 

Your primary options are Married Filing Jointly (MFJ) and Married Filing Separately (MFS). 

 

A very unlikely (but possible) option is Head of Household (HOH). Married individuals can be considered unmarried for HOH if all of the following apply:

• The taxpayer lived separate from his/her spouse for the last six months of the year (If you just got married in July, it's unlikely this is the case).Temporary absences are considered as time lived in the home.
• The taxpayer does not file MFJ
• The taxpayer paid over 1/2 of the cost of keeping up a home
• The taxpayer's home was the main home of the taxpayer's child, stepchild, or foster child for over 1/2 the tax year
  • The taxpayer claims this child as a dependent, or the child's other parent claims the child as a dependent under the rules for children of divorced or separated parents.

If you were legally married at the end of 2019 your filing choices are married filing jointly or married filing separately.  You cannot file Single.

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 $24,400 (+$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.

 

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-separately