# Glossary of invoicing and business terms Browse clear definitions and comparisons of common invoicing, quoting, and estimating terms. A practical reference for freelancers and small business owners. Regional tax and compliance glossaries are available for Australia, Canada, New Zealand, and the United Kingdom. Canonical page: https://invoicemama.com/glossary ## Terms - [ACH Payment](https://invoicemama.com/glossary/what-is-ach-payment): What is an ACH payment? Batch bank-to-bank transfers in the U.S. Covers credits, debits, timing versus wires and cards, risk controls, and net 30 invoices. - [Employer Identification Number (EIN)](https://invoicemama.com/glossary/what-is-an-ein): What an EIN is, who needs a federal tax ID, how it differs from an SSN or ITIN, how to apply for free with the IRS, and where it appears on invoices. - [Form W-9](https://invoicemama.com/glossary/what-is-a-w9-form): What Form W-9 is, who completes it, how payers use it for 1099s, 24% backup withholding when TIN rules fail, four-year IRS retention guidance, and FAQs. - [Invoice vs Quote vs Estimate](https://invoicemama.com/glossary/invoice-vs-quote-vs-estimate): Invoice vs quote vs estimate in 2026: fixed price vs range vs payment request. When to use each, comparison table, workflow, checklists, and FAQs. - [Net 30 Payment Terms](https://invoicemama.com/glossary/net-30-payment-terms): Net 30 means full payment is due within 30 calendar days of the invoice date unless your contract says otherwise. Covers 2/10 net 30, net 15 vs net 60, FAQs. - [Retainage (Construction Retention)](https://invoicemama.com/glossary/what-is-retainage): Retainage holds back part of each approved progress draw until closeout. Compare deposits, net terms, pay apps, waivers, release rules, and typical AR mistakes. - [Retainer Fee (Work Retainer)](https://invoicemama.com/glossary/what-is-a-retainer): What is a retainer fee? It buys reserved capacity for a period through recurring invoices. Compare hourly vs fixed fees, deposits, net 30, rollover FAQs. - [What is a credit note](https://invoicemama.com/glossary/what-is-a-credit-note): A credit note lowers an open invoice balance after returns, price fixes, or discounts. Compare memos, debit notes, revised invoices, and U.S. checklists. - [What is a pro forma invoice](https://invoicemama.com/glossary/what-is-a-proforma-invoice): What a pro forma invoice is for U.S. sellers, how import rules use it, how it differs from quotes and final invoices, and checklists to avoid payment confusion. - [What is a purchase order](https://invoicemama.com/glossary/what-is-a-purchase-order): A purchase order (PO) is buyer-issued authorization to buy goods or services at agreed prices. Learn PO numbers, invoice matching, blanket POs, and mistakes. - [What is a work order](https://invoicemama.com/glossary/what-is-a-work-order): Work orders align crews and billing before you invoice. Compare them with POs and invoices, link net terms, and use checklists and FAQs for US small businesses. - [What is accounts receivable](https://invoicemama.com/glossary/what-is-accounts-receivable): Accounts receivable (AR) is money owed from billed sales on credit. Compare AR vs AP, aging, net 30 due dates, collections habits, and common billing mistakes. - [What is Cost-Plus Pricing?](https://invoicemama.com/glossary/what-is-cost-plus-pricing): Cost-plus pricing adds an agreed markup to documented costs. Compare fixed price and T&M, see invoice lines, net 30 timing, and FAQs for US service businesses. - [What is invoice factoring](https://invoicemama.com/glossary/what-is-invoice-factoring): Invoice factoring converts invoices to cash via a factor. Compare recourse, notices, and fees with invoice financing, U.S. checklists, FAQs, and net 30 context. - [What is Time and Materials Billing?](https://invoicemama.com/glossary/what-is-time-and-materials-billing): Time and materials billing pays documented labor at agreed rates plus materials as work progresses. Compare fixed price, caps, invoices, and FAQs. ## Regional hubs - [Australia](https://invoicemama.com/glossary/au) - [Canada](https://invoicemama.com/glossary/ca) - [New Zealand](https://invoicemama.com/glossary/nz) - [United Kingdom](https://invoicemama.com/glossary/uk) ## Frequently asked questions ### What is the Invoice Mama glossary for? The glossary is a reference hub for invoicing, quoting, estimating, and small business payment language. Each entry explains a term in plain English so you can read contracts, invoices, and client emails with more confidence. ### Who is the glossary written for? It is written for freelancers, contractors, and small business owners who want quick definitions without accounting jargon, plus anyone comparing similar terms such as net 30 versus due on receipt. ### How do I find a specific term? Browse the alphabetical list on the glossary hub, then open the entry that matches your term. Each page focuses on one concept or a focused comparison so you can scan the answer quickly. ### Does the glossary cover payment timing and late fees? Yes. Many entries cover payment terms, due dates, reminders, and common wording you see on invoices and quotes. Always align final language with your policies and, when needed, professional advice. ### Are glossary pages a substitute for legal or tax advice? No. Definitions are educational. Laws and practices vary by location and industry, so use the glossary to build vocabulary and ask a qualified professional when decisions have legal or tax consequences. --- Invoice Mama is invoicing software for contractors, freelancers, and small businesses. It is not a tax, legal, or accounting firm. For current pricing, use the live pricing page. **More:** [Home](https://invoicemama.com/) - [Pricing](https://invoicemama.com/pricing) - [Guides](https://invoicemama.com/guides) - [Tools](https://invoicemama.com/tools)