The Invoicing SOP

Purpose

Define how completed work becomes an accurate invoice, sent fast. A standard operating procedure (SOP) is the written, repeatable process everyone follows the same way, so billing does not depend on who got around to it. Slow, sloppy invoicing is where earned money leaks out of a shop. An invoice that goes out days late gets paid days later or gets forgotten; an invoice with the wrong parts or a missing line gets disputed and sits. The two enemies of a service shop's cash are the invoice never sent and the invoice sent wrong. This SOP kills both by making billing a same-cycle, checked, repeatable step.

Scope

Applies to producing and sending customer invoices for completed work:

• Service, repair, and maintenance jobs
• Installation and project jobs, including progress billing
• Warranty and callback visits, billed or zero-billed for the record

Excludes recurring or contract billing on a fixed schedule (a separate automated process) and estimates, which precede the work.

Roles and responsibilities

Procedure

Step 1: Confirm the job is complete and documented

Do not invoice a job that is not finished and recorded. Before billing, confirm the work is done, the required photos and notes are attached, and any customer sign-off is captured. Invoicing an incomplete or undocumented job is how a dispute starts, because the invoice claims more than the record supports.

Step 2: Pull the labor, parts, and other costs

Gather every billable element from the job record:

• Labor: the time actually logged, at the correct rate
• Parts and materials: what was used, from the job's part usage
• Other direct charges: trip or dispatch fees, permits, or subcontracted work per policy

Bill from the job's real record of work, not from memory or a round guess. A part used but never logged is revenue given away.

Step 3: Apply pricing and tax correctly

Apply the right price tier for that customer (standard, member, or commercial) and the correct tax treatment for the customer and the work. A tax-exempt customer billed tax, or a taxable job billed none, both create rework and a correction later. Let the system resolve the tax rather than typing a number.

Step 4: Review before it goes out

A second look catches the error the customer would have caught:

• Every line matches the work performed
• Quantities and rates are right
• The math and the tax total foot
• The customer, address, and any PO reference are correct

The review is short. The dispute it prevents is not.

Step 5: Send it promptly, in the cycle

Send the invoice within the shop's stated timeframe after completion, ideally same day or next business day. Every day an invoice waits is a day the payment waits behind it. Send it through the customer's preferred channel so it reaches a person, not a dead inbox.

Step 6: Record the invoice and set the terms

Log the invoice in the system with its due date and payment terms. The open invoice now lives on the accounts receivable (AR) aging, the report that shows what is owed and how old it is. An invoice sent but never recorded is money owed that nobody is tracking.

Step 7: Hand off to follow-up

Once sent and recorded, the invoice enters the collections cadence: a reminder as the due date nears, and follow-up if it ages past terms. Billing's job ends at a recorded, sent invoice with a clear owner for the follow-up.

Records and retention

Keep invoices with their supporting job records and payment history for the period required for tax and dispute purposes, commonly several years. They are the backbone of the books and the proof behind any collection.

Common invoicing failures

• Billing an undocumented job. The invoice claims more than the record supports.
• Unlogged parts or labor. Earned money is quietly given away.
• Wrong tax treatment. Every one becomes a correction.
• Late send. Payment lands late or never.

References

• IRS Publication 583, Starting a Business and Keeping Records
• SBA guidance on invoicing and accounts receivable management
• See related: The Daily Payment Reconciliation SOP
• See related: The Quality Check Before Closeout SOP