The drama began on the night of 19 June when Royal Bank of Scotland discovered what was described as a computer glitch, which was preventing payments to and from accounts at NatWest, RBS and Ulster Bank. The botched software upgrade has affected millions of people, both the bank's own customers and those expecting payments from accounts held by these banks. The problems have affected savings and offset mortgages as well as current accounts.
The Guardian's investigations suggest things began unravelling when the bank updated a key piece of software called CA-7.
The bank was quick to deny suggestions that the "offshoring" of IT jobs to India had led to the problems. However, technology website The Register claimed a serious error committed by an "inexperienced operative" – who may be based in India – caused the meltdown.
RBS/NatWest/Ulster Bank customers The unprecedented meltdown meant millions of customers were unable to see how much money was in their accounts and whether bills had been paid. It left a defendant behind bars over the weekend after his bail money failed to arrive, and resulted in at least one family being forced out of their home. Some customers said they had no option but to take out payday loans to cover costs.
On 28 June, with the crisis into its 10th day, it was clear that while normal service had resumed for some, other people's finances were still in chaos.
Customers continued to relate their tales of woe on NatWest's website forum. "Anyone know what is happening? A cleared balance of £400 but my available balance is nil? I'm panicking as my mortgage is due to be paid and my hubby's wage is in tomorrow [29 June]. Things seemed OK at last, and now this?" said one poster from West Yorkshire. Another, in Nottinghamshire, said: "I have just been to the bank and yet again for the second week no wages, so is the problem not fixed …"
A customer in Brighton added: "I just called the hotline to find out why the cheque I paid in Monday was not showing and was told that anything paid in at the start of the week was stuck in a backlog and they hoped the money would be in my account some time late next week."
On 27 June, the bank said "the vast majority" of customers' account balances should be up to date, and that the "small amount" of outstanding unprocessed transactions was continuing to reduce.
It said future payments, such as salaries, should also be processed as usual.
But it emerged that as many as 100,000 customers with Ulster Bank have been told they will not have access to their money until Monday 2 July at the earliest.
Non-customers Many of those caught up in the fiasco aren't even NatWest/RBS/Ulster Bank customers, but have been hit financially because their employer banks with the group, and their wages did not appear in their account on time.
There have been reports of people unable to buy food or pay their rent. Some people have told of direct debits being returned unpaid because of lack of funds, triggering late payment charges.
Which? says other banks should treat customers who have been affected by the problems "positively and sympathetically". Anecdotal evidence suggests this has been happening, with reports of charges being waived where late salaries had resulted in payments not going through and charges being incurred.
One high street bank told Guardian Money it was keeping a tally of these costs and would be passing them on to NatWest/RBS. The bank, which didn't want to be named, said there had been cases where people hadn't been able to complete their house purchase, so it had stepped in.
"The funds didn't come through but we knew they were there, so we covered it in the knowledge that we will get the money back from NatWest. There were quite a few cases where that happened on Friday [22 June]."
Another high street bank told Money that tens of thousands of its customers had been hit by the technical issues.
"We did see some increase in call volumes from customers late last week and over the weekend, but call volumes have now returned to normal," the bank told us on Wednesday.
Small businesses NatWest alone has almost one million small business customers, and it emerged that some were paralysed by the RBS/NatWest fiasco, finding themselves unable to pay salaries or invoices.
The 200,000-member Federation of Small Businesses (FSB) says people running small firms that bank with the group, and who have experienced problems, should first of all go to their branch or call the bank.
They may later want to approach the Financial Ombudsman Service.
"Throughout this process, it is also advisable that small firms check with those who are expecting money to see if they have received it," adds an FSB spokeswoman.
What the bank is doing NatWest/RBS this week extended opening hours in hundreds of branches. Many will be open on 30 June from 8am until 4pm.
The banking group said it had arranged for customers to be advanced cash over the counter in cases where they had run out of money and needed to make payments.
Current account customers with a NatWest, RBS or Mint credit card "in good order" have been able to withdraw up to £100 over their limit without incurring fees or charges – although some will be levied but then refunded.
Complaints, refunds and compensation The bank promised that "no customers will be out of pocket as a result of these issues", adding: "We can confirm that any fees and charges incurred by customers will be fully refunded. This includes charges levied by a third party – for example, if you were late paying a non-RBS credit card or mortgage because your account wrongly showed there wasn't sufficient cash."
But as Money went to press, the bank hadn't said much about whether it will be compensating non-customers.
A spokeswoman told the Guardian: "We have been talking to other banks about how to cover any costs incurred by non-customers. We have agreed that anyone affected should speak to their own bank in the first instance."
NatWest/RBS customers who want to make a complaint should go to bit.ly/QrQvnF or bit.ly/N75xL2. If you are not a customer, go to bit.ly/N75Ghx or bit.ly/QrRbta
Consumer body Which? advises those affected to lodge a formal complaint "as soon as possible". It adds: "Give the bank a detailed account of any costs that you have incurred and payments that have been missed, both to and from your account. Also, be sure to stress the impact on you of any distress or inconvenience."
The bank has up to eight weeks to resolve your complaint. After that, you can go to the Financial Ombudsman Service.
When the ombudsman upholds a complaint, its aim is to put the customer into the financial position they would have been in. There is no automatic entitlement to extra compensation for disruption caused, and nothing in the rules that requires the bank to pay for non-direct losses, such as someone missing the chance to buy flights at the price they wanted.
In some cases the ombudsman will make an award for "non-financial loss", that is for "pain and suffering, damage to reputation, distress or inconvenience".
The impact on people's credit ratings NatWest/RBS claims that there should be no adverse impact to credit ratings. But those caught up in the fiasco may wish to check their credit record over the coming weeks to make sure their rating hasn't been damaged.
Those about to apply for a loan or mortgage should be especially vigilant.
Credit reference agency Experian says the banks have promised that any adverse data caused by the IT problems will not be sent to them. However, in the case of non-NatWest/RBS customers, creditors might not spot the root of the problem before data is sent to the agencies.
It costs £2 to get a copy of your credit file, and it is unclear whether NatWest/RBS will reimburse these fees. An alternative is to sign up for a 30-day free trial of the credit monitoring service offered by Equifax or Experian – but remember to cancel your membership before the 30 days are up, or you will incur a monthly fee.
