How do you delete customers via the app?

Hello Liam-magmawave-m, 

Welcome to the Community page, 

You can't delete a customer you can only make them inactive in the system. 

However it is not possible to delete/ make inactive a customer on the app version, this has to be done on the web browser version instead. If you have a look at this article it has all the steps you need to do to make your customer inactive.