Tap-in gates decide your fare after the journey

Tapping a card at a gate does not buy a ticket. It records an event, and the fare is worked out later by a system reconciling those events into journeys.

The gate records, the back office prices

Each tap creates a timestamped record at a location. Nothing is charged at that moment, because the system does not yet know where the journey will end.

Overnight, the records are matched into journeys and priced against the fare table, then aggregated into a single charge against the card.

This is why a bank statement shows one amount for a day's travel rather than a list of fares, and why the amount appears a day or more after travelling.

Capping is the reason the arithmetic fails

Most contactless systems apply a cap: once a rider's travel in a day or week reaches the price of a pass, further journeys are not charged.

The cap is applied during reconciliation, not at the gate, so a traveller cannot tell mid-day whether the next journey will cost anything.

Caps usually depend on the zones actually used, so a single trip to an outer zone can raise the cap for the whole day above what the earlier journeys implied.

An unmatched tap becomes a maximum fare

If a journey has an entry record and no exit, the system cannot know how far the rider travelled. It defaults to the highest fare that entry could have generated.

This happens through open gates, broken readers, or exiting a station where tapping out is not required in a network where it is. The rider does nothing wrong and is charged the most.

These charges are generally refundable on request, but the request has to be made, and the window for making it is limited.

Two cards break the cap

Capping is calculated per card. Using a phone for one journey and a physical card for the next splits the travel across two identities, and neither reaches the cap.

The same applies to two travellers sharing one card where the system expects one tap per person, which produces an unmatched entry and a maximum fare.

Digital wallets add a further trap, since a card and its phone version can register as separate tokens on some networks and as one on others, with no visible difference at the gate.

Where a paper ticket still wins

Contactless pricing is designed around urban commuting patterns. A single long journey, or travel that leaves the contactless zone, is often outside the capping structure entirely.

Checking whether a destination sits inside the contactless boundary is the one piece of homework worth doing, because the penalty for leaving it is charged rather than refused at the gate.