While CIMB's promo rates are one of the most competitive out there, computing for the bonus interest is a bit confusing. There are also conditions that need to be satisfied before you qualify for the bonus interest, and that some of them are capped at a certain ADB.

The bonus interests, including the 12%, have been credited already today. It actually only amounts to 9.5% of the ADB difference because the 2.5% portion has been credited last January 1 as base interest.

Aside from the calculator, the Excel below includes an illustration of how the 6 and 12% interest rates are broken down, the formula (CIMB uses 360 days instead of 365!), and the promo mechanics. The interest generate already includes the withholding tax, so it should match the amount you see in CIMB. Just download a copy of the Excel so you can edit.

https://1drv.ms/x/s!Apqxb9QmfBNziFM5J5NzTakTT2mw?e=iv88AB