Cash application is the work of taking each customer payment and applying it to the right open invoices. A check might pay three invoices and part of a fourth; a bank transfer might arrive with only a name in the memo.
Unapplied cash makes the aging wrong: customers look further behind than they are, and collection calls go to people who have paid. Remittance advice, lockbox files and bank memos all help, but some payments still need a person to decide where they go.
In APFoodz incoming payments are matched to customers and invoices.