The 810 replaces a paper or PDF invoice with structured data. The header (the BIG segment) carries the invoice number, invoice date and related PO number. Lines (IT1 segments) list each item billed with quantity, unit of measure and unit price. Allowances and charges, such as freight or promotional discounts, follow, along with payment terms and the total amount due (the TDS segment).
The invoice normally comes last in the order flow: purchase order, PO acknowledgment, advance ship notice, then the 810. The buyer matches it against the order and the receipt in a three-way match before approving payment. The payment, and the explanation of what was paid, may then arrive as a remittance advice (EDI 820).
Invoice errors delay cash. Prices that differ from the PO, quantities billed but not received, missing references and wrong charge codes cause an invoice to fail matching or be rejected. Unresolved differences become short payments, claims and deductions or a credit/debit adjustment (EDI 812), all of which take much longer to settle than an invoice that was right the first time.