Down payment requests are not the same as invoices as they can be issued without prior delivery of goods or services. When the down payment is received and posted, it clears in full the down payment request document even if the amount received is lower. The received amount is classified as a "contract liability" and is not recognized as revenue at that moment but is classified as deferred revenue. Down payments are reflected in Accounts Receivable in the balance sheet.
When the project is billed, AR down payments are reversed against the billed amounts until they are completely cleared. This eliminates the "contract liability" and deferred revenue created by the down payment.
On account payments are actual revenue received but not considered as billed revenue, rather they are applied against open invoices reducing the outstanding balance due from the customer. On account payments are reflected as "deferred revenue" in the balance sheet as the goods or services for which the payment is done are still not delivered or billed. The received on account amounts are posted on a G/L account called "on account issued". These amounts are actual income but are automatically deferred through a negative entry in an "on account utilized" account to avoid recognition.
When billable items are generated in the work package, the revenue they generate is recognized(EBRR) and create in the balance sheet a positive "on account utilized" posting and clears the "on account issued".
