[PennyPincher]

I'm not certain, but I'll provide a response just based on my experience, and assuming you still left money in the account after your withdrawal... (my disclaimer)

Let's say you had $20,000 in your account at the start of the month. (aaaahhh, lovely) You take out $15,000 on the 15th. You should earn a full month's interest on the $5,000 left, and 1/2 month's interest on the $15,000 that was withdrawn, since it had accrued interest.

So, if the interest rate is 3%, I would imagine you would earn:

monthly interest on the $5,000: $12.50 (5,000 * .03 / 12 months)

monthly interest on the $15,000: $18.75 (15,000 *.03 /12 months/2)

Total monthly interest: $31.25

Banks may likely reserve the right to not pay the interest earn on money withdrawn during the month, that's why I recommend to check w/your bank ~