Collecting fees is the part of running a dojo that nobody trained for. These guides cover how martial arts schools in the US and Europe actually get paid: recurring card payments, SEPA direct debit mandates, what to do when a payment fails, and how to set prices and membership tiers without losing students. Start with the payment collection guide for the full picture, then read the article that matches your problem. Figures are given in both dollars and euros, and every article says where its numbers come from.
