I have recently taken over a subscription box eCommerce business. My question relates to how to account when customers pre-pay for their subscription. So for example, lets say the customer pays for a 12 month subscription. The payment is taken in full immediately, but the contract will be fulfilled monthly, as one box will ship for each of the 12 months. Do we account for the VAT at the time the payment is taken, or do we need to spread it across the length of the contract?