Monthly excise payment for small scale industries allows deferred monthly settlement with recordkeeping and penalties for default. Rule 173GG permits SSI manufacturers to pay central excise duty monthly from 1 June 1999; eligibility follows value based SSI exemption notifications and a manufacturer already enjoying exemption in the current year retains the monthly facility even if current year clearances exceed the limit. Manufacturers must notify the jurisdictional officer, assess duty consignment wise and record duty payable in RG 1; invoices must state 'WORKING UNDER RULE 173GG' and show total duty payable. Monthly duty is summed and paid by the 15th of the next month from RG 23A/23C or PLA. Interest and daily penalty apply for delays with an overall cap tied to value of clearances; two defaults in a year disqualify continued use. Quarterly returns and a deeming provision preserve modvat credit for downstream users.