I bought the procreat app 2 years ago and yesterday on my new iPad when I install it again , it took me 12£ again 😔, why???

A question: do you use the same Apple ID?

Get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK) 

Is the current version the same app or a minimal update of the version that you bought?

Or is the current app a major paid upgrade?

M1 Mac mini, macOS 13.3.1;  Watch, series 7 GPS/cellular, watchOS 9.4; iPad Pro 2nd Gen, iPadOS 16.4.1; iPhone 12 Pro, iOS 16.4.1; TV 4th Gen, tvOS 16.4.1; HomePods, audioOS 16.4.1 and Airport Express w/ Airplay 2