Commonwealth Bank of Australia (ASX: CBA) said it is fixing the late processing of accounts, which has left some retail and business customers unable to access accounts.

The incident follows last month's technical problems at competitor National Australia Bank, wherein a corrupt file caused late payments for thousands of customers.

"The Commonwealth Bank has identified the cause of the late running overnight file and is currently in the process of finalising its processing into customer accounts," CBA said in a statement.

Earlier today, CommBank said a file scheduled to be processed overnight had not been completed, affecting "some business customers and a small number of retail access."

"At most, up to five per cent of CBA accounts are impacted."

"We expect that the processing of the file may cause some minor, short-term disruption to CommBiz and NetBank customers as we update balances in affected accounts."

"We are working on this as a matter of priority," CommBank said.

Shares in CBA were trading 0.97 per cent lower at $50.70 against a flat benchmark index just before midday.