I recently completed my deferred federal taxes and was expecting to pay penalty and interest since I owed. P&I weren't mentioned during filing. Should I wait?

[Critter]

The TT programs ONLY computes estimated underpayment penalties based on the information you entered  ....  if any was calculated  it was included on the return already ... review the return.  

Once you file the fed/state will bill you for any additional underpayment penalties, failure to pay or file penalties plus any interest they feel is required ... wait for the bill.