What it says on UOB stash account:
“Monthly Average Balance refers to the summation of each day-end balance in the Stash Account for each calendar month divided by the number of calendar days for that month.
To check if you qualify for bonus interest, your MAB will be compared between 2 months. If the difference between your previous month’s MAB and your current month’s MAB is zero or higher, you’ll get bonus interest.”
So example:
1. Last month a deposit of $100k into stash account was made on the 1st of that month (1 April)
2. You get your interest of say $250 on 1st of this month (1st May)
3. You choose not to withdraw your interest on 1st May but say on 10 May.
4. The amount you can withdraw from stash on 10 May then is $250, since all your day end balance will still be greater or equal to the summation of daily balance/ no of days for that month (Apr).
5. However, this day end balance for May will now be slightly higher (because the daily balance for 1 May to 9 May is $100250) so the June interest to be withdrawn would have to adjusted to allow for these additional day end balances to the monthly average balance of May.