Pay At Pump! How Does It Work?

I have seen various posts around the Monzo Community to do with Pay At Pump but none that really explain how it works.

When I am at home I use the same petrol station every single time, Morrison’s and up until today I would always get a £1 charge pop up in Monzo and it would sit there for around 48 hours before the final amount came in and the £1 would go away or get updated with the final amount.

Today I visited the exact same Morrison’s that I always go to put my card in the pump and authorized with my pin and as expected got the £1 charge, I filled the car up and almost as soon as I put the nozzle back down the final amount came through as a notification and the £1 was removed or updated.

This isn’t a problem I am just curious as to how this actually works technically is someone able to explain how these Pay At Pump systems work in the way they submit transactions to the bank because it seems to differ quite a lot.

Same mechanism that can reserve £1/£100 can finalise the amount within seconds. For fuel dispensing the mastercard rules say they must do, but vendors are lazy.

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What should happen is that when you insert your card it asks Monzo does this person have £99 quid available, it goes yes, or nope but they have £x, or nope if £0.

The pump then either says max £99 (or a partial amount of they have less available) or cancelled.

Once it finishes the pump should then immediately make a second request with the actual amount so you aren’t left with £99 pending.

However in reality I think it’s still the case <1% actually follow the spec set out years ago.

So most are still auth and holding £1 pending for a few days and then it actual is sent days later.

Whenever you buy something that’s like a coffee where you are present and being handed the goods it’s a single transaction (auth+capture). With something like fuel where it could be any amount it’s split into two an auth (to check and hold the amount) which gives back a token that’s later used to then capture the amount once known.

The auth and hold of a specific amount just means the pump knows they will good for that amount, so if they are holding £1 but fill up £50 they could be down £49 when it comes to asking for £50. The £99/partial means they wouldn’t lose out as you can only fill what you have.

They did trial this back in 2018 but it failed miserably as pumps weren’t sending through the final amount quick enough so people where having multiple £99s held for days which you can imagine pissed a lot of people off.


This is great - thank you for taking the time to write this up :slight_smile: