Do Britons (and I assume Canadians, Australians, etc.) All Have To Get New Passports Now?

But at least for the US, every note ever printed is still legal tender meaning I could take a 1863 15¢ note and use it as 15 cents in a store. Very different than currency that is valid meaning I can exchange it for a current bill.

Interesting, can the store refuse to accept it if they’re unsure of its legality?

Also, I realise US bank notes pretty much never get redesigned, but do they have additional security features added and have the materials used changed in line with current security standards you find in other country’s bank notes?

They can refuse to accept any denomination for any or no reason. As in English law, the concept of legal tender has nothing to do with shopping.

It’s only the $1 and $2 bills that never get redesigned. The others have changed a couple of times since the late 90s, with new designs and security features. The base material is still the same though, and it’s unlikely that it will change.