@Leo N wrote:
This is the info from IRS (which makes no distinction between a divorce and a separation):
"If you're legally separated or divorced at the end of the year
You must file as single for that tax year unless you're eligible to file as head of household or you remarry by the end of the year."
(https://www.irs.gov/individuals/fi[product key removed]-divorce-or-separation#:~:text=If%20you're%20....)
The type of "legal separation" that allows you to qualify to file as single is very rare and in practice, no one qualifies. I have read some tax court cases on this. Basically, you need a final order of separation, that says (1) you are separate forever, (2) can never get back together, and (3) any financial arrangements must be final. Most separations fail test 2 and 3, because financial orders are usually considered temporary until the divorce is finalized, and modern marriage and divorce laws usually allow for the parties to reconcile, and a separation where reconciliation is legally possible (even if very unlikely) is not "final" enough under the guidance of the Tax Court.
The fact that you did not get audited for filing single last year doesn't mean it was legal or that you won't get audited in the future (the IRS has 3-6 years to audit you depending on the circumstances, and California has at least 4 years to audit you.)
