CPF Annual Limit $37,740. If I expect to exceed this limit, Should HR adjust CPF contribution on Additional Wage (AW) paid in Jan? Or less contribution should be adjust on OW at year end?

AW is once a year or multiple times? HR should usually adjust on their own, since they would know whats the expected OW.

Typically, CPF contributions on additional wages are adjusted as soon as you’re about to hit the annual limit. But some employers do it by adjusting ordinary wages later in the year, best to check with HR.