What is this $15.81 Itunes charge for?
I am being billed $15.81 per month for something, and i cannot find anywhere in my itunes account information what this is for?
To see an account's purchase history : See your purchase history in the iTunes Store on a Mac or PC - Apple Support
If it's happening every month : View, change, or cancel your subscriptions - Apple Support
If you are a family organiser in family sharing it may be on one of the members accounts, so you may need to check their accounts as well.