Today, I received the letter from the Inland Revenue Authority of Singapore (IRAS) with my tax assessment. However, I wasn't expecting them to state that I don't have to pay any tax, they stated for tax payable $0.00

I checked with our HR manager, and we found out that she had transmitted my salary information to IRS under my old Foreign Identification Number (FIN), whereas I filed my taxes under my new (current) one. So basically, IRAS was not aware of any income for my new FIN, only for my old one.

I called IRAS, and luckily the officer was able to help me immediately, they're going to merge my 2 accounts and send me a new letter with the (hopefully) correct tax I have to pay.