1. Taxes can change quickly, and it's a pain in the ass to keep up with. If you're now needing to deal with changing the printed price on tens, hundreds, thousands of items - I can't even imagine.
2. Online sales you won't even be able to calculate it until the customer puts in their shipping information. And no, they can't figure that out beforehand as there are a myriad of reasons why where their IP is does not mean where it's being shipped to, which is where the taxes need to be calculated.
I'm curious, do books have prices printed on them in the UK? Here in the US, the suggested retail price (pre-tax, obviously) is generally printed by the manufacturer on the back or inside the dust cover of every book.
Gotcha. In the US, if you tried to keep that system, you’d need a different printed MSRP per tax nexus and books in warehouses would no longer be fungible.
2. Online sales you won't even be able to calculate it until the customer puts in their shipping information. And no, they can't figure that out beforehand as there are a myriad of reasons why where their IP is does not mean where it's being shipped to, which is where the taxes need to be calculated.