The principle behind the TAT is based on the following:
(a). If the transaction is a ‘credit-push’ funds transfer and the beneficiary account is not credited while the debit to originator has been effected, then credit is to be effected within the prescribed time period failing which the penalty has to be paid to the beneficiary;
(b). If there is delay in the initiation of a transaction at the originator bank’s end beyond the TAT, then penalty has to be paid to the originator.
(c). A ‘failed transaction’ is a transaction which has not been fully completed due to any reason not attributable to the customer such as failure in communication links, non-availability of cash in an ATM, time-out of sessions, etc. Failed transactions shall also include the credits which could not be effected to the beneficiary account on account of lack of full information or lack of proper information and delay in initiating a reversal transaction.
Here is the link to RBI circular 20-sep-19Harmonisation of TAT using authorised Payment Systems.PDF