Start with a reconciled balance
Enter the amount outstanding immediately before the first listed transaction as the opening balance. A negative opening balance represents a customer credit. Each row increases the balance by its charge and reduces it by its payment or credit. Rows are calculated in the order you enter them.
Example: an invoice and a payment
Begin with 200 outstanding. Add a 500 invoice, then a 300 payment. The running balances are 700 and 400. Give each entry its date and reference so the customer can locate the supporting document.
Opening balance: 200.00 INV-052 charge: +500.00 → 700.00 Payment reference PAY-18: −300.00 → 400.00 Closing balance: 400.00
A summary, not a new invoice
This tool does not pull transactions from your invoice library or bank. Enter verified records, sort them chronologically yourself and use one currency per statement. Avoid adding a total invoice and its component items as separate charges, which would double-count the amount.