Actually if you didn't need to show lease, you don't need to pay anything. I kind of remember that I didn't have residency certificate, so I showed them the lease. But all this was a long time ago well before Covid.
But by the book every landlord is supposed to stick those tax stamps on a lease, but noone does. So when they see a lease without tax stamps, they stick them on and then you pay what supposedly the landlord has to pay.
Probably when you have a residency cert they don't ask for a lease.