After you file

How did you request it ?    Did you go online at www.IRS.gov and fill in the installment agreement as directed by TT ?   If you did then the IRS may have agreed to the proposed plan on the spot or mail you a notice usually within 60 days.  So you can go online and check on your account to see where you stand in the process ... but a word to the wise ... expect the first payment to happen anytime so leave enough in the account at all times so it is not overdrawn and the installment agreement is voided.