I have 3 payment cards: 2 debit cards with different banks to spread risks, and 1 credit card. I have been using them all for months if not years by now at various places both offline and online without problems, but currently none of them are signed on the back for a very stupid reason, namely because I don't own any pens that are able to cleanly write on them.
I've tried reliable Bic pens, I've tried quality Parker pens with swappable ink cartridges, I've tried those cheap pens companies give away by the hundreds at events or markets,... Either they do not leave any ink behind when I try to write with them on the card (they do write on paper), or the ink they leave behind doesn't dry and smudges or even wipes off when I touch the card after writing. One of the cards even has a tiny bit of heavily written text left from when I first tried to sign it and failed to convincingly write my name, though by now that text has already dried.
The problem is that I don't want to keep trying pens and run the risk of damaging the card in some way. And I have NEVER had problems with these cards not being signed, because either it's a machine processing payments, or I'm paying through a payment app, or I'm paying online, or the salesperson just doesn't notice it, so I haven't seen the need to sign them yet, even though they're technically not valid unless signed.
Is there some sort of pen that's better suited for writing on the sort of material that these cards are made of?