Apply the Payment

Apply the Payment

A customer wires one lump sum that is supposed to cover "the old invoices, minus the early-payment discount we agreed on". In Business Central that reconciliation is the Apply Entries engine; your job is that engine distilled to its core algorithm: walk the open invoices oldest-first, honor payment discounts while their window is open, split the money across partial applications, and account for every cent — including the ones you hand back.

Requirements

The starter contains a table named "Open Invoice" — the in-memory ledger your code works on. Keep its fields and keys exactly as shipped; the grading tests seed it and read it back:

• "Invoice No." — Code[20], the primary key
• "Posting Date" — Date
• "Remaining Amount" — Decimal, what is still owed; 0 means the invoice is closed
• "Pmt. Discount Date" — Date, the last day of the regular discount period
• "Pmt. Discount Amount" — Decimal, the discount granted when the invoice settles inside its window

Create a codeunit named "Cash Application" with one public procedure:

procedure ApplyPayment(var OpenInvoice: Record "Open Invoice"; PaymentAmount: Decimal; PaymentDate: Date; GraceDays: Integer): Decimal

Rules:

1. Process the invoices oldest first: ascending "Posting Date", ties broken by ascending "Invoice No.". The physical order of rows in the buffer must never influence the result.