https://internet.ocbc.com/onlineform/publiconlineform/Form?FormId=CASATopUp2026
If the interest only counts from Feb 2, 2026 for 88 days, here's the revised calculation:
Interest earned:
- Amount: S$100,000
- Rate: 1.80% p.a.
- Period: 88 days (Feb 2 - Apr 30, 2026)
- Interest: S$100,000 × 1.80% × (88/365) = S$433.97
Effective annual rate: Your total holding period is from Jan 15 (deposit date) to May 31 (interest payment date) = 136 days
- S$433.97 / S$100,000 × (365/136) = 1.16% p.a.
The effective rate remains the same at 1.16% p.a. because while you deposited on Jan 15, you're tying up your funds for 136 days total but only earning interest for 88 of those days. The 18-day gap (Jan 15 - Feb 2) where you earn no promotional interest reduces your overall return.