On the 28th of September, it was reported in the UK's mainstream media -- TheSun, DailyMail, DailyExpress, BBC -- that access had been suspended to HSBC, Barclays and TSB's online banking website and mobile apps, leaving customers locked out of their accounts. No reasons, as of yet, have been given for the outages, HSBC stated "We will be conducting an investigation into the cause of this issue". With that in mind, I will examine some of the reasons given -- by the banks themselves in their Internet Banking legal agreement, who do state their service is not available 24 hours a day, 7 days a week -- for suspending / restricting access to Internet banking.
(a) the security of the customers bank account is deemed at risk
(b) the bank suspects unauthorised use of the customers security details
(c) the bank suspects fraudulent use of the customers Internet Banking
(d) a device the user connects with is not recognised, or has been technically modified to perform in an unusual way
(e) if access to the account has to be restricted due to a legal requirement
(f) if access to the account has to be suspended due to a regulatory requirement
(g) if the bank suspects the customer has provided false information about themselves
(h) if the bank suspects the customer has provided false information about another bank account holder
(i) a bank system failure has occurred
(j) if a third party the bank is contracted with has failed to supply a service to the bank in question
(k) any reason that is beyond the reasonable control of the bank in question
(l) if the bank ends the legal agreement with the customer
(m) occasional updates, repairs, or maintenance to the banks system
(n) if the bank customer is using an outdated browser or are using a version of an app
The above system outages from HSBC, Barclays and TSB would fall into reason (i) a bank system failure has occurred. The most common reason why access will be suspend will be reason (m) occasional updates, repairs, or maintenance to the banks system. It is fairly typical of banks to perform maintenance once per month, but it is usually performed during night time, to affect as few customers as possible, and the banks will typically provide prior warning.
One question posed by bank customers, is whether their expenses will be covered by the bank for any potential losses when access to their account is suspended. This is a difficult question to answer, the banks will usually state something like the following "We wont be liable to you if you suffer any loss in such circumstances" if the account is suspended for any of the reasons listed above.
If a customer is out of pocket due to a bank system crash, they should document the loss -- receipts, dates, times etc -- and contact the bank, they may reimburse the customer out of goodwill. Failing that, the customer could file a complaint with the Financial Ombudsman Service, the result of which is not clear.