A customer-invoicing SOP should define when a bill may be created, the approved inputs, who reviews and sends it, how payments are matched, and how exceptions are resolved. This is accounts receivable; use the supplier invoice-processing SOP for bills you receive and pay.
Write the operating sequence
| Stage | Required instruction |
|---|---|
| Trigger | The actual contract event: delivery, accepted milestone, deposit request or recurring billing date |
| Prepare | Retrieve the customer, agreed scope, rates, tax treatment, terms and prior billing or deposits |
| Draft | Generate the invoice through the controlled numbering system and check the calculation |
| Review | Obtain the approval required for this amount, scope and version |
| Send | Use the agreed contact or portal and retain the issued record and submission evidence |
| Reconcile | Match payments and adjustments to the invoice; distinguish gross payment, fees and net settlement |
| Follow up | Apply the actual due date, communication policy and dispute route |
| Retain | Link the invoice, approval, payment and correction records in the approved location |
Assign the responsible role and permitted backup for each stage. Do not insert a new deadline or approval limit while documenting the process.
Make billing variants explicit
Milestones: identify the contractual milestone and required acceptance evidence. A project’s progress percentage does not automatically establish the amount billable.
Deposits and retainers: record the agreed charge and how it will be applied. Check previous amounts before the final invoice so the same work is not billed twice.
Recurring billing: verify the current service period, price and any pause, cancellation or renewal instruction before release. A recurring template still needs a route for changes.
Credits and disputes: keep the original issued record, route the decision to an authorized person, and use the supported correction process. Do not assume that every correction requires voiding the invoice or that every dispute automatically stops all collection activity.
Walk through a worked handoff
In an illustrative project, the service owner records acceptance of milestone M2. The biller retrieves that approval, checks M2 has not already been invoiced and drafts the amount specified in the contract. The authorized reviewer checks the exact draft before it is sent. The payment record later references that invoice ID.
The important evidence is the connection between accepted work, billed amount, approval and payment. Page count does not establish that the handoff is complete.
Validate the SOP before release
Try a normal invoice, a changed scope, a missing approval, a partial payment and a duplicate-send attempt using permitted sample records. Confirm the expected stop or escalation at each unresolved condition.
Use the pre-send invoice checks, refund and credit examples and due-date worksheet as supporting material. Choose a billing system only after identifying what the current workflow cannot control reliably.
Required invoice fields, tax handling and retention are jurisdiction-specific. The responsible finance owner should approve those rules before the SOP is used.
See Also
If you want to move from general advice into actual product choices, start with Invoice Processing SOP: 7 Steps, Template and Controls, How to Write Effective SOPs for Office Teams, and What Does CRM Pipeline Mean? A Simple Guide.
For a wider picture after the basics, Best Document Scanner for a Paperless Small Office: 4 Picks and CRM for Beginners: A Simple Guide for Small Business Teams are the next places to read.