I've come off the Elizabeth Line at Paddington, needing to transfer to TfL Rail/GWR to Hayes.
I've misread the platform number at Paddington, touched in, realised I can't actually access my train, touched out then touched in at the correct gateline.
[...]
Full journey by Rail/Tube is Farringdon to Hayes and Harlington.
*If* you travelled from Farringdon to Paddington on the same contactless card, then you would have tapped
1. In at Farringdon
2. Out at the Elizabeth Line or London Underground gateline
3. In at a National Rail gateline
4. Out at the same NR gateline
5. In at another NR gateline
6. Out at Hayes & Harlington
and I would expect that steps 2 and 3 become linked together as an Out-of-Station Interchange as it is between EL/LU and NR gatelines, but the same might not have happened between steps 4 and 5 (
as MikeWh's website does not list Paddington NR to NR as an OSI). The result would then be that you are charged a single journey 1-4 (Farringdon to Paddington NR) and a separate journey 5-6 (Paddington NR to Hayes & Harlington), and, since there are no incomplete journeys, I believe no adjustment will be made. (I have done exactly this kind of manoeuver, but with 3,4,5 all at the same gateline, at other stations to deliberately break an OSI.) If this turns out to be the case when you check your journey history later, then you would have to contact the helpdesk to ask for a refund of the fare difference (but check first that you wouldn't end up paying the same anyway or even more, due to caps, peak/off-peak, etc).
If you were using an undiscounted adult Oyster then it should be resolved overnight and any credit refunded next time you touch in/out.
If you Oyster has a discount of any sort then you may need to contact the helpdesk tomorrow.
Not relevant for contactless, but my naive assumption was that, provided you initially touched in and out within 2 minutes of each other, this refund of the maximum fare onto the Oyster card would occur immediately when you touch in at the next gateline within 45 minutes (or equivalently, this touch simply reopens the journey without subtracting a new maximum fare) - is this not the case? (A delayed refund might have consequences for someone with only enough Oyster balance for one journey, which would go negative after the in-and-out maximum fare is deducted and might prevent the next entry.) I note that TfL's website does not state when the refund happens (
"If you re-enter the same or a different station within 45 minutes, you'll be refunded") but yours seems to imply it does occurs immediately upon the next touch (
"However, if you re-enter (after topping up for instance) within 45 minutes the original maximum fare is refunded and a new journey is started")?