Automatic creation of PIN and SIN ID's when using the bulk import tool

Having to manually create ID's when doing bulk imports of PIN/SIN is a real pain. I'm also finding that it will still duplicate the numbers, even if you try to make them run consecutively. Example:

Last bill ID is PUR000050

I import 100 bills, manually setting the ID's at PUR000051 onwards

I then go to create my next bill through the system as normal but instead of it being PUR000151 it duplicates PUR000051 and so on. End result is ID's will end up getting used twice.