What is the postgres sql command for last_user_id ???

I would like to know whether there is any command which the server will give the
record ID back to the client when client puts the data and the server generates
an autoincrement ID for that record.
For example if many clients try to put the money data to the server and each
record from each client has its own record ID by autoincrement process of the
server [x+1] and i don't need to lock the record since it will bring the system
to slow down. That client wil then want to know which ID that server gives to
that record in order to select that record to print the reciept [bill].
I know that in mysql there is a command "last_record_id" which acts the same as
I mention above. Does anybody know that , please give me the detail?

Amrit,Thailand