I set up an installment agreement through TT and I'm having payments debited from my checking account. Do I have send in a check for line 8 on form 9465?
Turbo tax had me print out a voucher to send in my initial payment (from line 8). Do I need to send that in a check with voucher or not?
Yes, you may send a check or money order for the initial payment. Send your payment to the address listed on the payment form. Here is more information regarding installment agreement payments https://ttlc.intuit.com/questions/4004473-installment-payment
