Q. How does asset cash increase?
An asset cash increases (debited) as well as a liability unearned service revenue increases (credited) by USD 4500. The credit is to Unearned Service Fees relatively than Service Revenue because the USD 4500 applies to more than just the current accounting period. Unearned Service Fees is a liability for the reason that if the services are never performed the USD 4500 will have to be refunded. If the payment had been there for services to be provided in December the credit would have been to Service Revenue.