In this intricate economic climate I have to hand it to Link, which is right up there in complexities. I'll try to explain.

Rajendra Patel first rang me in November from Crossroad Stores in Witham in Essex, to say that he had received no commission from Note Machine for three months. It was being withheld until a discrepancy in ATM funds had been recovered.

Apparently, a customer said she had tried to take £240 out of Rajendra's machine at 7.14am on October 24. She later claimed that she didn't get her money (although she did not raise this point in the store where Rajendra can always be found at that time of day). The printout of the transactions showed that the machine did pay out. However, after she complained the money had been taken from her bank, Link reversed the transaction and Rajendra was told he therefore still had the £240.

He disputes this. "We balance every day and I have never had an amount over like that. This happened once before three years ago when TRM was the ATM company. I sent in my electronic journal and eventually TRM said I was right. The customer had made a false claim."

I spent quite a while talking to Note Machine, which did its damnedest to solve the riddle and sent me a lot of documentation, but came to the conclusion that it could only uphold the Link regulations. They are very complex - the manual runs to 2,000 pages.

I also spent some time mulling over my conversation with Note Machine's spokeswoman and I have spoken to the retailer again. Neither of us can understand why the machine's documentation does not show the reversal. Note Machine says that Link can reverse transactions within a couple of hours, but the printout I was sent didn't show any reversal of that particular transaction even though it shows about 12 hours-worth of transactions on that day.

Rajendra is fairly sure that the customer, who used to be a regular at that time of day for top-ups, bill payments, newspapers and so on, would have made a fuss when the machine apparently refused to cough up. Is it beyond reason to think that she then went to her bank, claimed the card hadn't worked and got the money back (or got the money twice)? Rajendra says he has not seen the woman since.

Clearly, the system does have its flaws - as in this case - but was it one mistake or two?

Note Machine tells me that the process for claims is due to be simplified in favour of the customer this May. "The new claims process will be more automated, with the acquirer being required to provide greater evidence before a claim can be refused. The status of the claim will be visible by Link, the issuer and the acquirer. The new process will also include an arbitration stage should a claim not be settled equitably," says Note Machine.