your IF() statement seems incomplete?

=IF('Sheet2'!A:A,A2,SMALL(('Sheet2'!B:B),2))

=IF('Sheet2'!A:A....is what?

the IF() syntax is...
=if(criteria-to-test,what-to-do-if-test=TRUE,what-to-do-if-test=FALSE)

Based on that, you have your criteria, but are not testing it?

Also, if you are using a range like that, it is probably an array formula and needs to be entered with CTRL SHIFT enter, not just enter


It's hard to offer suggestion without seeing any data though