In the Netherlands gaps aren’t allowed either, and I’m surprised that it is elsewhere, as that allows to you get rid of unwanted invoices whenever you want.

However you are allowed to have multiple sequences, differentiated through a prefix, but all starting at 0. That’s what we recently did to switch invoice generation tools (we actually still run both of them alongside each other atm).

Of course you could still drop some invoices from the end when you do this, but I guess tax authorities accept that risk.