To set an expiry date for the users account with useradd, use the -e option.
e.g.
Bash:
useradd -e 2020-12-31 someuser
The above example will set the expiry date of 31st December 2020 for the account of a user called someuser.
Obviously, if you're setting up a new user, you might want to use several other options, not just the -e option.
A quick bit of duckduckgo-fu yielded this, which will probably help you out a lot. And probably explains things better than I could!
In Linux, a 'useradd' command is a low-level utility that is used for adding/creating user accounts in Linux and other Unix-like operating systems.
www.tecmint.com