Final answer:
The account affected when a customer pays in advance for services to be performed in the future is the Unearned Revenue account.
Step-by-step explanation:
When a customer pays in advance for services to be performed in the future, the account that is affected is the Unearned Revenue account. Unearned Revenue is a liability account that represents the amount of money received in advance from customers for goods or services that have not been provided yet. It is important to record this payment as a liability because the services are still owed to the customer.