Funny what an adult beverage will do :-(

Should be

=A1-DAY(A1)+33-DAY(A1-DAY(A1)+32)

but now it's longer than the DATE function.

=DATE(YEAR(A1),MONTH(A1)+1,1)

<sigh

--ron

If shorter is better, what about....
=EOMONTH(A1,0)+1