Return deadline for married filing jointly - one spouse is current living overseas

[DTNY07]

I have a client that got married during 2021 (she has been a client for 20 years as a single filer). Her husband had lived overseas the last two years.  Both are US citizens.  If they file jointly, is the deadline 6/15 or 4/18?  While she did stay overseas for part of 2021, she was a US resident the entire year

[rbynaker]

Why not just file an extension by 4/18?

[DTNY07]

If i have all the data and the return is due 4/18, i would do it before then.  But, if i can push it off to 6/15, that gives me more time to get to the ones due 4/18