Where tax is paid at 11:00 P.M. on 20th October 2017 and filed returns on the same day. If for any reason the amount is credited to the account of the appropriate Government on 21st October 2017, will it amount to default

The date of credit to the account of the appropriate Government in the authorized bank shall be deemed to be the date of deposit in the electronic cash ledger. Therefore, in this case the date of payment/deposit of tax shall be 21st October 2017, which means a delay of one day in payment of tax.

(ICAI FAQ PUBLICATIONS 06-09-2017 TAX PAYMENT, INTEREST, PENALTY AND OTHER AMOUNTS: FAQ NO. 16)