Bank may credit to the account any sum deposited by the Accountholders or any other person, notwithstanding that the sum is made payable to one Accountholder only.
The Bank may likewise reverse any credit or debit to the account that is made in error, subject to clearance of such reverse payment or, if clearance would not be possible, subject to any debit balance immediately being made good by the Accountholders.

Банк также/аналогичным образом может сторнировать любую ошибочную проводку по дебету или кредиту счета при условии проведения полных расчетов по обратному/встречному платежу или, в случае невозможности проведения расчетов, - при условии незамедлительного покрытия дебетового остатка владельцами счета.

Думаю, что где-то так.

"notwithstanding that the sum is made payable to one Accountholder only" -- here they are talking about the following example situation:

Both my wife and I are joint holders of our bank account. My wife deposits a check made out (or as banks say "made payable") to her. My name is nowhere on the check, only my wife's name. Despite that, the bank would credit our account with the amount of that check "notwithstanding that the [check] is made payable to [my wife] only," and not to both of us.

Also, both my wife's and my employer electronically deposits (wires) our paychecks into our bank account every other week. The electronic transfer from my employer would have my name in the "pay to" field. The check from my wife's employer would have her name in that fiels. But our bank would deposit both of those checks into our joint account. And both my wife and I would have access to those funds, regardless of who deposited them and regardless of to whom those funds were payable. In other words if the amount is intended only for one of the account holders, the bank would still deposit that amount into the joint account.

imho, it would be smth like "даже если сумма была предназначена только для одного из владельцев."