Proper procedure is to take full payment for final month's rent and then issue a separate payment back to the tenant for security deposit return. (law.stackexchange.com)
Average endowment plans deliver a return of 4 - 5 %, which is lower than bank fixed deposit returns. (securenow.in)
You also can get your security deposit returned as long as you pay your balances off in full every month, on time. (valuepenguin.com)