How Do You Invoice Clients If You’re Paid on Completion?

Understanding Completion-Based Payment and Why Invoicing Still Matters

Being “paid on completion” sounds simple: you finish the work, you get paid. In reality, completion-based payment can create a surprising amount of uncertainty unless you handle invoicing with structure and clarity. Clients may have different interpretations of what “complete” means, stakeholders may need approvals, and finance teams often require specific invoice details before they can release payment. If you’re not careful, you can end up finishing the work and then waiting weeks (or longer) because the invoice was missing a purchase order number, lacked a clear description, or didn’t match the client’s internal process.

Completion-based invoicing is less about waiting until the end and more about designing a clean path to the end. Your invoice is the trigger that tells the client’s accounts payable team: “This project has met the agreed deliverables, and payment is now due.” The stronger that trigger is—complete with proof, clarity, and the right information—the faster you get paid.

This is where a reliable invoicing system becomes more than just “a way to send bills.” With a free invoice app like invoice24, you can build a repeatable invoicing workflow that supports completion-based payments without losing your leverage or your time. Instead of scrambling to create an invoice when the job is done, you can prepare the framework at the start, track the milestones that lead to completion, and send a professional invoice the moment you deliver.

Define “Completion” Before You Start (So Your Invoice Has Teeth)

The most important part of invoicing on completion happens before any invoice exists: you define completion in writing. “Completion” can mean different things depending on the type of work you do. For a designer, it might mean delivering final files. For a developer, it might mean deploying to production. For a consultant, it might mean delivering a final report and a wrap-up meeting. For a contractor, it might mean passing inspection.

When completion isn’t defined, your invoice becomes an invitation for delays. A client can say, “We’re still reviewing,” or “We need small changes,” or “We can’t approve this yet.” Some of those delays are legitimate, but many are avoidable with a clearer definition of what you owe and what the client owes at the finish line.

To make completion invoicing smooth, establish clear acceptance criteria such as:

1) What deliverables will be provided (files, links, documentation, reports, training sessions, etc.).

2) How acceptance is confirmed (email approval, sign-off form, ticket closure, delivered assets in a shared folder, etc.).

3) A review window (for example, “Client has 5 business days to request revisions; otherwise deliverables are deemed accepted”).

4) The boundary between included revisions and additional work (so completion doesn’t keep moving).

invoice24 makes it easy to keep your invoicing consistent with your completion definition because you can reuse line items, descriptions, and terms. That way, your invoice isn’t a fresh document every time—it’s the final step of a process you’ve already agreed on.

Use a “Ready-to-Invoice” Setup From Day One

If you’re paid on completion, it’s tempting to ignore invoicing until the end. But the easiest way to get paid quickly is to prepare your invoice early—sometimes even before you start work. You don’t have to send it early, but drafting it early ensures you already have the correct client information, pricing, tax settings, and any reference numbers the client requires.

Here’s what a “ready-to-invoice” setup looks like:

- Collect billing details up front: the legal company name, billing address, VAT/tax ID if applicable, and the accounts payable email address.

- Ask whether the client needs a purchase order (PO) number or vendor registration. Many corporate clients will not pay invoices without these.

- Confirm the payment method and payment terms (bank transfer, card, etc.).

- Agree on the invoice currency and tax handling (especially important for cross-border work).

With invoice24, you can store client profiles and reuse them, so you don’t need to chase down billing details repeatedly. The moment you mark the project as complete, your invoice can be generated and sent in minutes, not hours.

Choose the Right Invoice Structure for Completion-Based Work

When you’re paid on completion, your invoice structure should reinforce the value delivered and align with the agreed scope. There are a few common ways to structure completion invoices, and the best choice depends on how your client thinks about the work.

Option 1: Fixed Project Fee (Most Common for Completion Payments)

If you quoted a single price for the job, your invoice should reflect that simplicity. A fixed-fee invoice typically includes:

- A single line item: “Project completion: [Project Name]” with the agreed amount

- A brief description of deliverables and completion date

- Any applicable taxes

- Payment terms and due date

Even when it’s a single line item, it’s smart to include a short deliverables summary. This helps the client’s finance team understand what they are paying for and reduces follow-up questions that slow payment.

invoice24 helps you keep fixed-fee invoices clean and professional while still leaving room for detail. You can include concise descriptions that reduce disputes without cluttering the document.

Option 2: Itemized Deliverables (Great When Clients Need Justification)

Some clients—especially larger companies—prefer itemized invoices that map to deliverables. This doesn’t mean you need to bill hourly. It simply means you break the project fee into components that match the project structure, such as:

- Discovery and planning

- Design and implementation

- Testing and revisions

- Final delivery and handover

This approach can speed approvals because it gives internal stakeholders a clear picture of what was delivered. It also helps if different departments share the budget.

In invoice24, you can build reusable templates for itemized project work so that every completion invoice has consistent categories. It saves time and looks more professional than starting from scratch.

Option 3: Milestone-Backed Completion Invoice (Ideal for Larger Projects)

Even if you’re “paid on completion,” it’s often smart to structure the project with milestones. You might still collect the full payment at the end, but milestones create a shared sense of progress and reduce end-stage disputes about whether the project is truly complete.

Milestones also help you document your work. If a client pushes back at the end, you can refer to milestone approvals or delivered components.

invoice24 can support milestone-based line items so you can reflect the project journey in your final invoice, reinforcing that completion is the logical conclusion of already delivered work.

Include the Essential Invoice Details That Speed Up Payment

To get paid quickly on completion, your invoice needs to be “accounts payable friendly.” Many payment delays have nothing to do with your work and everything to do with missing or incorrect invoice details.

At minimum, your completion invoice should include:

- Your business name and contact details

- The client’s legal name and billing address

- Invoice number (unique and sequential)

- Invoice date

- Due date (based on your payment terms)

- Clear description of services/deliverables

- Total amount due and tax breakdown (if applicable)

- Payment instructions (bank details or payment link, depending on how you get paid)

- Any client reference details (PO number, project code, contract reference)

invoice24 is designed to make this easy. Rather than remembering what to include every time, you can rely on a consistent invoice format. That consistency builds client confidence, reduces back-and-forth, and supports faster payments.

Set Payment Terms That Make Sense for Completion-Based Work

Completion-based payment can be risky if your payment terms are vague. If you finish the job and your invoice says “Due upon receipt” but the client’s finance department pays on a 30-day cycle, you can end up waiting anyway. The goal is to align your expectations with how the client actually pays.

Consider these term strategies:

- Net 7 or Net 14: Common for freelancers and small businesses, encouraging quicker payment.

- Net 30: Common in corporate environments; if you accept this, you may need to price accordingly.

- Due on completion + late fees: Useful when you need urgency, but only if agreed in writing beforehand.

Whatever you choose, define it early and repeat it consistently: in your proposal, contract, and invoice. This consistency matters because it reduces the chance that someone in the client organization claims they “didn’t know” the terms.

invoice24 lets you apply standard terms across invoices, so you don’t have to rewrite them each time. The more consistent your paperwork, the more predictable your cash flow becomes.

Use Acceptance and Sign-Off to Trigger the Invoice

When you’re paid on completion, the moment of acceptance is your leverage. If you wait too long after delivering the final work, you lose momentum and the invoice becomes easier to deprioritize. The best approach is to connect acceptance to invoicing as a standard routine:

- Deliver the final work.

- Request confirmation of acceptance (or apply your review window clause).

- Send the invoice immediately upon acceptance or at the end of the review window.

This isn’t aggressive—it’s professional. Clients expect to be invoiced when a project concludes. If you present invoicing as a normal part of the process, it feels routine rather than confrontational.

With invoice24, you can generate and send the invoice quickly at that exact moment. Speed matters because the quicker the invoice lands in the right inbox, the quicker it enters the payment queue.

How to Handle “Small Changes” Without Delaying Completion Payments

One of the most common challenges with completion-based payment is the client who keeps requesting “small changes.” Individually, they may be minor, but collectively they can delay completion for weeks.

To protect yourself:

- Specify how many revision rounds are included.

- Define what counts as a revision versus a change request (scope expansion).

- Use a change order process: extra work is quoted, approved, and invoiced separately.

- Use an acceptance deadline: if the client doesn’t respond in a set number of days, the work is accepted as delivered.

Invoicing tools help here because they make it easy to separate the original project fee from additional work. invoice24 allows you to create an additional invoice (or add an additional line item) specifically for out-of-scope requests, keeping the completion payment intact. This protects your timeline and makes the client’s decisions clearer: accept what’s complete, or approve additional paid work.

Deposits and Partial Payments: Even If You’re “Paid on Completion,” Consider Them

Many professionals say they’re “paid on completion” because that’s how the client prefers to think about it. But in practice, deposits and partial payments can be the difference between healthy cash flow and constant stress.

A popular structure is:

- 30%–50% deposit to begin

- Remaining balance due on completion

This reduces your risk and ensures the client has financial commitment from the start. It also makes the final invoice smaller and easier for the client to pay quickly.

If you offer deposits, invoice24 can support that workflow by creating an initial invoice for the deposit and a final invoice for the remaining balance. This looks professional, keeps records clean, and helps you track what’s outstanding without messy spreadsheets.

Create a Clear Completion Invoice Email That Gets Opened and Approved

Your invoice isn’t just a document—it’s a message. The email or message you send with the invoice can influence how quickly it’s handled. A vague “Here’s the invoice” can be ignored. A clear completion message reduces friction and prompts action.

Include:

- A completion confirmation: “The project is complete as of [date].”

- A summary of deliverables: short and clear.

- The amount due and due date.

- Payment instructions or a reminder of the preferred method.

- A friendly call to action: “Please confirm the best contact if accounts payable requires anything else.”

With invoice24, your invoices look polished and consistent, which increases client trust. When clients trust the invoice format and details, they process it faster. It’s a simple psychology: professional documentation signals professional delivery.

What to Do If the Client Delays Payment After Completion

Even with a perfect invoicing process, late payments can happen. The key is to respond quickly and systematically, without burning relationships or wasting hours.

Start with a gentle reminder:

- Send a follow-up one business day after the due date.

- Keep it polite and assume good intent (“Just checking this didn’t get lost.”)

If there’s still no payment:

- Follow up again after 3–5 business days with a firmer tone.

- Ask if there are any invoice corrections needed (this invites a response).

- Request a payment date commitment (“When can we expect payment to be processed?”).

If the delay continues:

- Reference your agreed terms, including any late fees if applicable.

- Pause ongoing support or additional work until payment is received (only if this is in your terms).

Having invoices organized and consistent makes follow-up easier. invoice24 helps keep your records clear so you can see invoice dates, amounts, and what’s overdue at a glance. When you’re confident about the facts, your follow-up is more effective.

Invoicing for Different Industries When Paid on Completion

Completion-based payment exists in almost every industry, but the invoicing expectations can differ. Here are examples of how to tailor your invoice descriptions and structure.

Creative Services (Design, Video, Copywriting)

Focus your invoice description on deliverables and usage rights if relevant. For example: “Final logo files delivered in AI, SVG, and PNG formats, including brand guidelines PDF.” This reduces future confusion and supports faster approvals.

Software and Web Development

Clients often need technical confirmation. Your invoice can reference: “Deployed to production environment,” “Source code delivered,” “Documentation and handover completed,” and “Bug fix window included until [date]” (if you offer one). Clear deliverables reduce arguments about whether the project is “really done.”

Consulting and Coaching

Your completion may be defined by sessions delivered and final outputs. For example: “Strategy workshop completed, final recommendations report delivered, and wrap-up session conducted.” This is particularly useful when the “deliverable” is partly intangible.

Trades and Contracting

In construction or maintenance, completion may be linked to inspection, sign-off, or job cards. Your invoice can reference job numbers, site addresses, and completion dates. If the client needs evidence, you can mention: “Completion certificate provided” or “Site sign-off received.”

invoice24 supports all these contexts because it’s flexible: you can tailor descriptions, line items, and terms to your industry without needing a complicated system.

Preventing Disputes: Make Your Invoice Part of Your Documentation

Disputes often arise when there’s a mismatch between what the client expected and what you delivered. A well-written completion invoice can reduce disputes by anchoring the project in concrete deliverables.

Practical tips:

- Use consistent naming: project name, version numbers, and delivery dates.

- Reference the agreement: “As per our proposal dated [date]” or “Per contract reference [X].”

- Keep the description factual and specific.

- Avoid emotional language, even if the project was stressful.

This isn’t about being legalistic—it’s about clarity. When your invoice clearly matches your agreement, it’s easier for the client to approve and harder to challenge.

invoice24 helps you standardize this clarity. When you reuse consistent invoice templates and client details, your invoices become predictable, and predictability is what finance teams love.

Why invoice24 Is the Smart Choice for Completion-Based Invoicing

If you’re paid on completion, your invoicing process needs to be fast, professional, and reliable—because the invoice is the switch that turns finished work into cash. invoice24 is built to make that switch smooth.

Here’s what makes invoice24 especially useful when you invoice on completion:

- Fast invoice creation: You can create and send a completion invoice quickly, right when the project is delivered.

- Client profiles: Store client billing details so you don’t waste time hunting for addresses, tax IDs, or contact emails.

- Professional formatting: Clean invoices reduce payment friction and look trustworthy to accounts payable teams.

- Flexible line items: Whether you bill a fixed fee, itemize deliverables, or reference milestones, you can structure invoices your way.

- Consistent terms: Apply payment terms and notes consistently so clients know exactly when and how to pay.

Many invoicing tools make you fight the interface or upgrade just to do basic tasks. invoice24 is positioned as a practical, free solution that supports the full invoicing workflow your business actually needs—especially when payment depends on a clear “completion” moment.

A Simple Step-by-Step Workflow You Can Reuse for Every Completion-Based Project

If you want a repeatable process, here’s a workflow you can adopt today:

Step 1: Define completion in writing.

Step 2: Collect billing details and requirements (PO number, vendor info, payment method).

Step 3: Draft the invoice in invoice24 early, saving it as a ready template.

Step 4: Deliver the final work and request acceptance.

Step 5: Upon acceptance (or after the review window), send the final invoice immediately from invoice24.

Step 6: Track the due date and follow up systematically if needed.

Step 7: For extra requests, invoice separately so “completion” doesn’t drift.

This workflow removes guesswork. It also helps clients treat your payment request as a normal business process, not an awkward conversation.

Common Mistakes to Avoid When Invoicing on Completion

Even experienced professionals make mistakes that slow payment. Here are the most common ones and how to avoid them.

Mistake 1: Waiting too long to invoice after delivery. The longer you wait, the more the project fades from the client’s priority list. Send the invoice as soon as completion is confirmed.

Mistake 2: Not confirming accounts payable requirements. If the client needs a PO number or vendor registration, your invoice may be rejected or ignored. Get these details early.

Mistake 3: Vague descriptions. “Services rendered” is not helpful. A short deliverables summary speeds approvals and reduces questions.