Tax return... How and When?

Hello fellow expats, I am currently discussing a salary package with a company in KL. I have browsed through extensively here and at other sites. I still have questions that I cannot find answers for. Appreciate your clarification please.

For easy calculation sake, let's use -
a) RM10,000 as the monthly salary,
b) Jan 2018 as the commencement of the job, and
c) Obligation of the 14-days leave is observed.

I understand that the first 6 mths, it will be a flat tax rate of 28% and then follow by a tiered rate of 24%. Since it is deducted monthly, by the end of Dec, I would have paid (RM2800 x 6) + (RM2400 x 6). However, according to the income tax calculator on IMONEY.MY, I only am supposed to pay RM13,100 instead of RM31,200.

Questions -
1) First of all, is my above understanding correct?
2) If correct, when will I get my RM18,100 tax difference (RM31,200 – 13,100)?
3) If flawed, please help me understand my error(s).

Thank you!


Charlie