No, for taxes, married filing separately is a different category than single. Married filing separately results in a higher tax bill than married filing jointly for most couples.

Married filed separately effectively locks you out of a lot of benefits when compared to unmarried filing single, or married filing jointly.

Nope. It's a reason some might note get married.

There are places in the tax code where Single != Married Filing Separately.

One pertinent example is that Washington State's capital gains tax applies after $270k per single person, per married couple filing jointly OR split in half for married filing separately. Which could be a theoretical $18.9k/year difference in taxes.

Yeah, that particular deduction reeks of some big brain energy. My family is going to be outta here by the end of the year, hopefully.