GSTR-3B filing deadlines require TRAN-1 filing and cash payment conditions before final return submission. Notification prescribes last dates for furnishing returns in GSTR-3B for July and August 2017 by distinct classes of registered persons, distinguishing those entitled to input tax credit who opt to file or not file FORM GST TRAN-1. It conditions filing on prior computation and cash deposit of tax payable for July, filing TRAN-1 before GSTR-3B where elected, and payment of any excess tax in cash when GSTR-3B discloses a higher liability. Payment must be made by debiting the electronic cash or credit ledger as per the Act and rules.