Bank customers were left despairing as they experienced 90-minute queues on the phone amidst a last-minute rush of PPI claims.
A number of major banks also experienced website difficulties as the 11.59pm deadline approached last night.
But the Financial Conduct Authority (FCA) offered a glimmer of hope to those who faced challenges submitting complaints.
A spokesperson said the watchdog said it expected firms to treat people fairly and to take “a pragmatic approach” with complaints received soon after midnight.
That could mean those whose 11th hour efforts to make claims were hampered by technical issues will still have them investigated.
Santander apologised for its site going down for “essential maintenance” yesterday morning, while ongoing issues at NatWest and RBS limited their online capacity too.
Demand also brought down The Co-Op Bank’s online PPI enquiry form yesterday afternoon.
Those looking to make claims over the phone, meanwhile, faced lengthy waits for service, with some waiting as long as an hour-and-a-half to speak to Barclays and Santander.
A spokesman for Barclays blamed the delays on an “unprecedented volume” of calls.
The Financial Conduct Authority (FCA) said more than £33 billion had already been paid out to people who had complained about mis-sold PPI before yesterday’s closing date for claims.
The payment protection insurance was sold with products like loans, credit cards, finance arrangements and mortgages to cover repayments if the customer could not, through being made redundant or illness, disability or death.
But the FCA found many of the 64 million policies bought in the UK, mostly between 1990 and 2010, were mis-sold to people who, for one reason or another, could never have successfully claimed.
A spokesperson for watchdog said: “We have no plans to extend the deadline.
“This has been widely publicised and it is clear from the high level of consumer activity that the FCA and firms have seen, that people are well aware of the deadline.
“However, we expect firms to follow the principle of treating customers fairly.
“Where a firm knows that customers may have had trouble accessing their services – whether website or phone – in the run-up to the deadline, then we would expect them to apply a pragmatic approach to dealing with complaints received immediately after the deadline.”