how do i avoid the $40 charge on my MD state tax return ?

Are you using the Online web version or the Desktop program?   In the Desktop program it is $25 to efile a state return.  Then if you want the fee deducted from your federal refund there is an extra $40 refund processing service charge which you can avoid by paying with a credit card.  Go back though the FILE tab slowly and watch what you click on.  There is one screen that can trip you up.