I assume you mean to ask: can one spouse file as Married Filing Separately and the other spouse not file at all? Yes, it's possible, but you must file if any of the following are true:

1. Your gross income was at least $5 and your spouse files a separate return and itemizes deductions.

2. Your unearned income was more than $950.

3. Your earned income was more than $5,700.

4. Your gross income was more than the larger of —
a. $950, or
b. Your earned income (up to $5,400) plus $300.

It usually makes more sense to file as Married Filing Jointly - so I'm curious what the situation is that causes you to think this might be a good idea?

I suspect there may be past year tax liabilites for one spouse, possibly from a time prior to their marriage.