1: When there’s a preauthorisation, we capture the amount on the funding card. We do this because we don’t want to take the risk of being out of pocket, which could bankrupt us. The merchant has 7 days to collect preauthorised payments. If they don’t, the refund will be reflected in your funding account 2-3 working days after being processed.
2: If the bill ($100) and tip ($20) is processed in two transactions the preauthorised amount ($100) will be processed on the card we already captured the fund from and the tip ($20) is processed on the current funding card.
If the bill ($100) and tip ($20) is processed in one transaction ($120), which is typical for the USA, the total ($120) will be processed on your current funding card and the preauthorised for the bill ($100) is refunded to the respective funding card.
In the latter case, you can use the Go Back in Time feature to make sure the payment is on the funding card you wish to use
I’ve been surprised by the differences between countries. In some countries you can use your pin with contactless payment if it’s over the preauthorised amount, whilst in the UK you need to use Chip + PIN.
True In the Restaurant Case described above, the merchant tends to leave the bill (£100) be without sending a reversal.