Excise filing deadlines require periodic GAR and ER returns and timely electronic payments to maintain compliance. Assessees must submit specified GAR and ER forms according to prescribed monthly, quarterly and annual frequencies, with an electronic payment requirement for duty challans; ER returns distinguish non-SSI, EOU/STP and SSI filing schedules. Annual financial statements and principal input declarations arise where prior payments exceed a threshold, with changes to declarations to be notified within a short timeframe, invoice serial numbers intimated before use, and refund applications filed within one year.