Central Board of Indirect Taxes and Customs(CBIC) has issued a Notification No. 34/2018- Central Tax dated 10th August,2018 to specify the last date for filing of return in Form GSTR-3B for each of the months from July, 2018 to March, 2019.The return shall be furnished electronically through the common portal, on or before the 20thday of the month succeeding such month.
Every registered person furnishing the return in FORM GSTR-3B shall, discharge his liability towards tax, interest, penalty, fees or any other amount payable under the said Act by debiting the electronic cash ledger or electronic credit ledger, as the case may be, not later than the last date, as detailed in column (3) of the above Table, on which he is required to furnish the said return.
Source: Central Board of Indirect Taxes and Customs