It normally goes unchecked but they might ask and if it’s not signed they might not accept it.
On the backend I think it’s one of those things that can make them liable for chargebacks / fraud claims if the signiture doesn’t match. But then I don’t think Monzo or many / (any?) banks keep your signiture on file so no idea how that would be checked.
This would be against the retailer’s contract with Mastercard. There is a principle of acceptance that they would have agreed to in the contract, where they must accept all Mastercards if they have agreed to accept Mastercard at all - so they must accept any valid cards, which would include those without the strip. As has already been said, Mastercard have changed the rules of card design to remove the requirement for a signature strip.
You can report the merchant to Mastercard if they give you trouble or refuse to accept your card.
This is no longer true. To encourage retailers to adopt Chip technology instead of magstripe, a series of “liability shifts” were implemented (the deadlines of which have all passed, so in the US all transactions are now affected by them). Essentially, this shifts the liability for all fraudulent transactions where magstripe or signature authentication were used to the merchant. It is no defence for the merchant, in other words, to claim that they “checked the signature”. Therefore, they shouldn’t even bother to do it as it holds no value for them. They would be forced to foot the bill for fraudulent transactions anyway, as the argument goes that the fraud would have been prevented if they had bothered to upgrade to Chip technology.
I know we use Chip and PIN in the UK, and the US normally uses Chip & Sign, but the principle is the same.
It would be, but depending on how far into the woods you go, some retailers may not care about MasterCard regulations and one single complaint to MasterCard won’t be the end of their merchant contract (for example, I live in a town where there’s a restaurant I avoid because they surcharge debit cards as well as credit cards even though that’s not allowed either, and somehow they haven’t gotten the critical mass of MasterCard or Visa complaints to stop doing that even though they got some tourist traffic after an episode of Yellowstone was filmed there).
If OP is sticking to bigger cities, though, it shouldn’t become an issue. Much of the US has finally gone contactless so that’s probably the way to go.
Just back from 5 weeks in the US, major cities out West and then road-tripping East through all kinds of tiny towns…used my Monzo premium card all the way and never once had a problem over a spend of a couple of thousand pounds+, and across a mix of small and big amount on the card
Had to sign a couple of times, but obviously never checked, and card / exchange rate etc was rock solid the whole way. Really impressed