I am married. My wife had her taxes prepared. I was told by the preparer to file single. I don't read that as a legitimate option on Turbo tax site. What do I do?

That "preparer " is wrong, and should be called to task.  You cannot file Single if you were legally married as of 12/31/2020. How did your wife file, and why aren't the two of you filing Married Joint?

He probably said file Separate not Single.  Did you get married in 2020?

And may I ask why you are filing separate returns?  Sometimes people don't realize the differences between filing  Joint and MFS.

Unless you have a specific reason to file separate returns,

It is usually better to file Joint. Joint has the lowest tax rates and the highest Standard Deduction.   And if you are in a Community Property state MFS gets tricky to figure out.  Here's some things to consider about filing separately……

In the first place you each have to file a separate return, so that's two returns.  And if you are using the Online version that means using 2 accounts and paying the fees twice.  

Many people think they come out better when filing Married Filing Separate but they are probably doing it wrong.  If one person itemizes deductions then the other one must itemize too, even if it's less than the standard deduction, even if it is ZERO!  

And there are several credits you can't take when filing separately, like the

EITC Earned Income Tax Credit

Child Care Credit

Educational Deductions and Credits

And contributions to IRA and ROTH IRA are limited when you file MFS.

Also if you file Married Filing Separately up to 85`% of your Social Security becomes taxable right away even with zero other income.

See …….

https://ttlc.intuit.com/community/married/help/is-it-better-for-a-married-couple-to-file-jointly-or-separately/00/25590