i am toying with the idea of returning principle sum of loan back to OA (20k partial). then from OA transfer the same amt to SA to earn higher interests. i think the fall back of this is i couldn't get tax break out of this..
There's the rub. If you qualify for tax relief, the tax relief is valuable, and you really ought to grab it. So you could instead consider a $7K cash top up and a $13K OA repayment/OA to SA transfer in the scenario you describe. Or, if you're in the 11.5% income tax bracket for example, how about $7,000 directly into your Special Account and $13,805 of OA repayment and OA to SA transfer? The extra $805 is your income tax savings (11.5% of $7,000), meaning $20,805 added to your Special Account that "combo" way has an equal cost to you (somebody in the 11.5% tax bracket) of $20,000 added without the direct SA top up. Adjust slightly if you'd like to account for the fact that the $805 is paid in the future, in the form of a reduced income tax bill next year, but you get the idea, hopefully.
Yes, I know the top up plus accrued interest is committed to your future Retirement Account (and well rewarded), but don't plan/aspire to be poor, OK? And the immediate tax relief is valuable and helps you be less poor, as the above example illustrates.
Does it mean that when I pass on, my children sell the hdb (bought with my OA) and CPF will claw back all accrued interest and leave little sale proceed to my children?
No, that's not how it works.
So I should pay back loan principle when I can afford to do so, so that my children will get bigger sale proceed?
No, you should only pay back Ordinary Account dollars (and accrued interest) used for housing when that (your CPF Ordinary Account) is the next best available choice for your savings. That's not
often the case, but it is sometimes the case. For example, if you're approaching or at age 55, and if you've got thousands of dollars or more stewing in ordinary bank accounts and fixed deposits earning less than 2.5% interest, then chances are repayment into your 2.5% interest earning Ordinary Account is comparatively attractive. It might not be the
best available savings/investment choice -- "it depends" -- but it's certainly better than a 1.8% interest fixed deposit.