The Post Office has suffered another breakdown of its automated accounts system, which pays out pensions and other benefits.
Staff were authorised to make one-off cash payments
The network, first introduced in 2003, crashed for almost four hours in August, affecting 200,000 people.
Intermittent problems meant customers in various parts of the UK on Monday were unable to withdraw money from accounts or access benefits.
The Post Office said very few people should have been affected this time.
A spokeswoman said staff had been authorised to give one-off payments of £20 to account holders, so they were not left without cash.
The breakdown had affected a number of branches for 10-15 minutes at a time on Monday but its cause remains unknown.
The system, which also broke down for an hour in July, should be working as usual on Tuesday, the spokeswoman added.
About 1.7 million people access benefits, state pensions and the new tax credit payments using the Post Office.