I am filing married but want to do at a single rate.

[xmasbaby0]

Do you mean on your W-4?  You do that with your employer.

[Anita01 · Accepted solution]

You cannot make that choice on a tax return.  You do that on a W-4 for your employer to know how much tax to withhold from your wages.  Once you receive a W-2, the tax withheld reflects the choice you made on your W-4 and could result in your receiving  a larger refund or paying less tax owed than you would have if you had not made that choice on your W-4 for your employer.