Understanding standard invoice terminology prevents costly misunderstandings with clients, accountants, and tax authorities. These are the 12 terms that appear most frequently in commercial invoicing worldwide.
Net 30Payment due 30 calendar days from the invoice date. The most common B2B payment term globally. Net 7 and Net 14 are more common for smaller independent contractors and improve cash flow significantly.
Due on ReceiptPayment expected immediately upon receiving the invoice. Standard for first-time clients, one-time purchases, and any transaction where you have no established payment history with the client.
PO NumberPurchase Order number assigned by your client’s procurement department. Including it on your invoice speeds up their accounts payable approval process and directly reduces payment delays in enterprise clients.
VAT / GSTValue Added Tax (Europe, UK) or Goods & Services Tax (Australia, Canada). If registered in your jurisdiction, you must include your tax registration number and charge the applicable rate. Not including it on an eligible invoice is a compliance failure.
SubtotalThe sum of all line items before any discount, tax, or shipping is applied. This is the figure your client checks against their approved quote or purchase order. It must match exactly or the invoice may be returned for revision.
RetainerA recurring monthly fee paid in advance for an ongoing service commitment — typically invoiced as a single line item. Retainers provide predictable income for the service provider and guaranteed availability for the client.
Pro Forma InvoiceA preliminary invoice sent before work begins to confirm the scope, price, and payment terms. Not a request for immediate payment; used for client approval, customs declarations, and import documentation. Clearly label it “Pro Forma” to avoid confusion with a final invoice.
Credit NoteA document issued to reduce or cancel a previously issued invoice — typically used when a service is returned, work is disputed, or an invoice error needs correction. A credit note is the formal accounting mechanism for reversing an invoice; issuing a revised invoice without a credit note creates duplicate records.
Late Payment InterestInterest charged on overdue invoice amounts. In the UK this is governed by the Late Payment of Commercial Debts Act (8% over base rate). In the EU, the Late Payment Directive sets a minimum of 8% above ECB rate. In the US, rates vary by state. Stating your rate on the invoice enforces your right to claim it.
Accounts PayableThe department or function within your client’s organisation responsible for processing and paying invoices. Understanding that your invoice enters an AP workflow helps you format it with the reference numbers (PO, project code) that accelerate their internal approval process.
Invoice AgingA report categorizing outstanding invoices by how long they’ve been unpaid (0–30 days, 31–60 days, 61–90 days, 90+ days). A key metric for freelancer cash flow management. Invoices in the 61+ day category typically require escalated follow-up: a formal letter before action is standard at 90 days overdue.
2/10 Net 30A payment incentive term: 2% discount if paid within 10 days; full amount due in 30 days. Rarely used by freelancers but common in product-based businesses. The discount costs the seller 2% but accelerates cash by 20 days — equivalent to an annualised interest rate of approximately 36%.
