If you requested an installment agreement with the IRS on Form 9465, and
indicated that you’ll make an initial payment with your return, this initial amount
must be paid by check with the 1040-V voucher.
This is true even if you requested direct debit of future payments. The IRS takes 30 days (longer after March 31st)
to process the installment agreement request and begin the direct debit
payments.
