Invoice, Payment & Collections

What this guide covers

• Invoice numbering, customer details, work description, and contract references
• Due dates, deposits, retainers, milestone billing, and recurring invoices
• Sales tax and reseller documentation
• Payment methods, POS and online payments, receipts, and written confirmation
• Late follow-up, aging reports, and partial payments
• Disputes, refunds, credits, and chargebacks — handled lawfully
• A minimum viable accounts-receivable process

What every invoice must include

An invoice is not a polite reminder — it is a billing document that ties a specific amount to specific work or goods under a specific agreement. Without those links, customers delay payment because they cannot verify what they owe, and you cannot defend the charge if a dispute arises.

Each invoice needs a unique sequential number (INV-2026-0041), your legal business identity, customer billing details, invoice date, due date, and payment terms. The work-or-goods section ties delivery to the signed estimate, order, or contract: “Design and build — master bath, per EST-2026-018, approved 3/12/2026” or “Order #4471 — 60 units, per PO-2026-0210.” Use line items with quantities unless the agreement was explicitly fixed-price. Show subtotal, sales tax, total due, accepted payment methods, and any deposit already applied.

Deposits, retainers, milestones, and recurring billing

Deposits (often 25–50% before start) follow contract language on refundability once materials, inventory, or schedule are committed. Retainers work similarly for consultants and agencies — drawn down against hours or deliverables, with a running balance shown each cycle. Milestone invoices bill progress with running totals: “Contract $12,400 — invoiced $6,200 — this bill $3,100 — balance $3,100.” Product sellers use purchase order numbers and packing-slip references instead of milestones. Recurring or subscription invoices should show the billing period, renewal date, and any proration for mid-cycle changes. Final invoices capture the remaining balance plus approved changes, minus prior payments. Do not bundle disputed extras into a final bill, and do not continue past an unpaid milestone without a written decision.

Sales tax and reseller documentation

Sales tax rules vary by state, locality, product versus service, and whether you are the retailer or a service business buying materials or inventory. This guide cannot state your rate or filing obligation — but your invoice must reflect whatever your accountant or state revenue office requires.

If you collect sales tax, show it as a separate line with the rate or jurisdiction noted. If you do not collect tax on a category of sale because it is exempt or outside your nexus, say so in your terms or invoice footer so customers do not assume the omission is an error.

Reseller certificates and tax-exempt documentation belong in the customer file, not scattered in email. When a customer claims exemption, obtain the valid certificate before invoicing tax-free. Keep copies with the account record. Buying inventory or materials tax-free for resale and then failing to document the chain is a common audit trigger for small businesses of every kind.

Tax collected is not revenue — it is money held in trust for the state. Transfer it to a tax reserve account when received, not when the return is due. That habit prevents spending sales tax on payroll or equipment.

Payment methods, receipts, and confirmation

Offer methods customers actually use — ACH, check, card, POS terminal, or platform pay — but understand the cost and risk of each. Card and POS payments incur processing fees and carry chargeback exposure; checks can bounce; cash is immediate but hard to prove without a receipt. Pick a default and state it on the invoice or at checkout.

Record payments same day: date, amount, method, invoice applied, remaining balance. Send written confirmation and keep processor IDs, check numbers, or numbered cash receipts. Partial payments must show the open balance explicitly. Do not mark an invoice paid on “check in the mail” — align with your cashflow calendar so owner pay is not scheduled against money still in transit.

Late follow-up and aging

Follow-up is not optional — it is part of the service. Most late payments are administrative: the wrong person received the invoice, it went to spam, or accounts payable runs on the 15th. A calm, documented sequence solves most cases without damaging the relationship.

Day 0: invoice sent with due date and payment instructions. Day due + 3: friendly reminder referencing invoice number and amount. Day due + 10: second notice asking if there is a question or dispute. Day due + 20: firm notice stating the balance, that the due date has passed, and next steps if unpaid. Adjust timing to your terms — Net 30 accounts get a different calendar than due-on-receipt or point-of-sale customers.

An aging report lists open invoices by how late they are: current, 1–30 days, 31–60, 61–90, 90+. Review it weekly. One overdue $800 invoice is annoying; four overdue invoices totaling $11,000 is a cash crisis. Aging turns feelings into numbers.

Every contact goes in the account file: date, channel, who you spoke with, what was promised. “AP clerk said check runs Friday 5/10” is actionable. “They'll pay soon” is not. If a customer requests more time, confirm in writing: amount, new date, and that work on new phases pauses until terms are met if that is your policy.

Partial payments, disputes, refunds, and chargebacks

Partial payment without agreement creates ambiguity. If a customer sends half the invoice with no explanation, do not assume acceptance — contact them the same day. Apply the partial payment to the invoice, document the remaining balance, and ask whether the short payment reflects a dispute. Silence lets a customer later argue they paid in full.

Disputes fall into a few buckets: scope or order disagreement (“that wasn't included” or “that's not what I ordered”), quality complaint, billing error, or cash shortage dressed as a complaint. Separate them. Scope and quality disputes need reference to the signed estimate, change orders, and photos or delivery records — which is why closeout and delivery documentation matters before you invoice. Billing errors you should fix quickly and reissue. Cash shortage may need a written payment plan — not more work or product shipped on credit.

Refunds and credits should follow a written policy stated at sale or in the contract: full refund window, partial refund for work already performed, store credit versus cash refund, and restocking terms for returned products. Apply refunds to the original payment method where possible and document the reason.

Card chargebacks happen when a customer asks their bank to reverse a charge — common in both e-commerce and service billing. Your defense is documentation: signed agreement or order confirmation, delivery or fulfillment proof, communication showing acceptance, and your refund policy. Respond to processor notices within the deadline — missing it loses by default. Reduce chargeback risk by not surprising customers with charges, describing line items clearly, and resolving complaints before they escalate to the bank.

Never offset a disputed amount by withholding a customer's property, cutting off active service illegally, or publishing customer details. Those tactics create legal exposure far beyond the unpaid invoice.

Lawful escalation — and what to avoid

When polite follow-up fails, escalation paths depend on amount, jurisdiction, and relationship. Options may include a formal demand letter, mediation, small-claims court, collection through a licensed agency, or an industry-specific lien where applicable and lawful (mechanic's liens are one example, specific to certain trades). Each option has cost, timeline, and relationship consequences. There is no universal “send it to collections” button that fixes bad documentation.

Unlawful tactics include harassment, threats, misrepresenting authority, public shaming, unauthorized fees, and ignoring valid dispute requests. Consumer and commercial collection laws vary, but fraud and harassment are never acceptable. Use licensed collectors with written agreements; consult an attorney before liens or lawsuits. Prevention beats escalation: clear agreements, milestone or upfront billing, and pausing work or shipment when terms break down.

Minimum accounts-receivable process

Accounts receivable (AR) is the system that tracks what customers owe and whether you have applied their payments correctly. At minimum: one invoice template, one numbering sequence, one place to log sent invoices and due dates, and one weekly review block.

When you send an invoice, log the invoice number, customer, amount, date sent, due date, and status (open, partial, paid, disputed). When payment arrives, match it to the invoice the same day and update the status. When follow-up happens, note it. That spreadsheet or software habit is AR — not a fancy ERP.

Connect AR to owner compensation. Revenue on paper is not money you can pay yourself. See Owner Pay System — owner draws should come from collected cash, not from hope that overdue invoices will land before rent is due.

Common mistakes

• Invoicing from memory without a contract, estimate, or order reference
• Combining multiple jobs or orders on one invoice so the customer cannot reconcile
• Treating deposits or prepayments as earned revenue before work is performed or goods ship
• Marking an invoice paid when a check is “in the mail”
• No follow-up because chasing money feels awkward
• Continuing work or shipping more product while prior milestone invoices are unpaid
• Surprise line items on a final invoice that were never change-ordered or approved
• Threatening or shaming customers instead of taking documented lawful steps
• Spending collected sales tax on operating expenses

When professional guidance may be needed

Consult a qualified attorney when considering liens, significant B2B collection lawsuits, or any response to a customer's legal threat. Consult a CPA or bookkeeper when sales tax nexus, exemption certificates, or bad-debt write-offs affect your filings. Use licensed collection agencies only with a written agreement and verification they comply with applicable law. If a customer alleges billing fraud or files a chargeback above your documentation ability, professional help early beats losing by default.

Related Business & Systems resources

• Work Lifecycle & Closeout System
• Records, Files & Document Control
• Cashflow Calendar for Operators
• Owner Pay System
• Tax Reserve System
• Business Bank Account Structure
• Business & Systems hub