How Do You Invoice Clients When You’re Paid Based on Performance or Results?

Why performance-based invoicing needs a different approach

Getting paid for performance or results can be one of the most rewarding ways to do business. When it works, it aligns incentives, reduces friction on price, and helps clients feel confident that they’re investing in outcomes instead of activities. But it also introduces a practical challenge that catches many freelancers, agencies, and consultants off guard: how do you invoice when the “product” is a result, and the amount due depends on what actually happened?

Traditional invoicing assumes a predictable price: an hourly rate, a fixed project fee, or a recurring retainer. Performance pricing doesn’t fit neatly into those boxes. The invoice has to connect the dots between an agreed performance metric, the proof that the metric was achieved, the agreed payout formula, and the time period the invoice covers. It also needs to be clear enough for the client’s finance team to approve without a long back-and-forth.

This is where having a flexible invoicing workflow matters. If your invoicing tool is clunky, you’ll waste time explaining charges, rebuilding invoices, and manually tracking performance data. If your tool is built for flexibility, you can invoice confidently, get approvals faster, and keep your relationship with the client focused on results. That’s exactly why invoice24 is a strong fit for performance-based billing: it’s designed to handle real-world invoicing needs without making you wrestle with the format.

What counts as “performance-based” payment?

Performance-based payment (sometimes called results-based pricing) is any agreement where the amount you earn depends on achieving defined outcomes. These outcomes can be measured in many ways, and the invoice needs to reflect whichever measurement you and your client agreed to.

Common performance-based structures include:

Leads or inquiries: You’re paid per qualified lead, booked call, form submission, or demo request.

Sales or revenue: You’re paid a commission per sale, a percentage of revenue, or a bonus for reaching revenue milestones.

Traffic or engagement: You’re paid based on visits, signups, downloads, watch time, or other engagement metrics.

Cost savings: You’re paid a share of savings you create (for example, reducing ad spend waste, cutting operational costs, or improving procurement).

Milestones and bonuses: You’re paid a base fee plus bonuses tied to hitting specific targets.

Hybrid performance + retainer: You receive a smaller monthly retainer for availability and execution, plus performance fees for outcomes.

Each structure affects how you present line items, how you explain calculations, and how you define the invoice period. invoice24 makes it easy to create invoices that match these structures, because you can tailor descriptions, add multiple line items, show formulas plainly, and include optional notes that make approvals smoother.

Start with the contract: your invoice is only as strong as your terms

Before you think about invoicing, you need terms that define what “results” actually mean. The invoice is the proof and the request for payment, but the contract is the authority that explains why the amount is due. If the terms are vague, you’ll end up with invoice disputes even if you did great work.

Make sure your agreement covers:

1) The metric: Exactly what is being measured (for example, “qualified leads” defined by specific criteria).

2) The source of truth: Which platform or report is authoritative (CRM, analytics dashboard, ad platform, affiliate software, call tracking tool, etc.).

3) The calculation: The payout formula (per-unit fee, percentage, tiers, bonuses, caps, minimums).

4) The time period: Weekly, monthly, campaign-based, or milestone-based.

5) Validation rules: How long leads must remain valid, what happens with refunds/chargebacks, how duplicates are handled, and any disqualification rules.

6) Payment timing: Net terms (Net 7, Net 14, Net 30), and whether there is a verification window before invoicing.

7) Dispute handling: A timeline for disputes and what documentation is required.

Once your terms are clear, invoicing becomes straightforward: the invoice simply reflects the agreement. With invoice24, you can keep your invoice wording consistent with your terms by saving standard descriptions and reusing them across invoices, which helps clients recognize the format and approve faster.

Choose the right performance invoicing model

There isn’t just one “right” way to invoice for results. The best model depends on what you’re measuring and how quickly those measurements stabilize. Below are the most common models, along with how to invoice them cleanly.

Model 1: Invoice per result (unit-based invoicing)

This is the simplest model: you’re paid a fixed amount per outcome (for example, £50 per qualified lead). You invoice at the end of the period for the number of outcomes delivered.

How the invoice should look:

Use a line item like:

“Qualified leads delivered (Dec 1–Dec 31): 42 leads × £50 = £2,100”

Tips to reduce disputes:

Define “qualified” clearly, and if possible include a short summary in the invoice notes: “Qualified = UK-based, requested demo, company size 10–200.”

invoice24 is ideal here because you can write line items in plain English and clearly show the quantity, unit rate, and total. That clarity is what finance teams want.

Model 2: Commission-based invoicing (percentage of revenue)

If you’re paid a percentage of revenue, your invoice needs to show the revenue number and the agreed commission rate, plus the period covered.

How the invoice should look:

“Commission on attributed revenue (Dec 1–Dec 31): £38,500 × 12% = £4,620”

Tips to reduce disputes:

Specify whether it’s gross or net revenue, whether VAT is included in the base, and how refunds are treated. If there’s a returns window, you might invoice based on “net settled revenue” from the previous month instead of the current month.

With invoice24, you can include a simple breakdown in the description and keep the invoice professional, readable, and aligned with your agreement.

Model 3: Milestone-based invoicing (bonuses for targets)

Milestone invoices work well when performance is “chunky,” like reaching a ranking target, hitting a subscriber threshold, or completing a measurable transformation.

How the invoice should look:

Line items might include:

“Performance bonus: Achieved 10,000 newsletter subscribers (milestone reached Dec 18) = £1,500”

Tips to reduce disputes:

Be explicit about what qualifies as “reached” (peak count vs. sustained count). If it has to remain above the threshold for 14 days, invoice after that period.

invoice24 makes milestone invoicing easy because you can create one-off invoices quickly, add milestone descriptions, and keep your invoice history organized for future reference.

Model 4: Hybrid invoicing (retainer + performance)

Hybrid models are common because they balance risk: you get consistent income to cover execution costs, and the client gets strong incentives tied to results.

How the invoice should look:

Use separate line items:

“Monthly service retainer (Jan): £1,000”

“Performance fee (Jan qualified leads): 30 × £75 = £2,250”

Tips to reduce disputes:

Keep the retainer description focused on scope (availability, management, execution) and keep the performance fee focused on measurable outcomes.

invoice24 is built for these real-world mixed invoices, and it’s especially useful when you want your retainer to stay consistent month-to-month while only the performance portion changes.

Decide when to invoice: monthly, milestone, or rolling?

Timing is one of the biggest questions in results-based work. Invoice too early and clients may say results aren’t “confirmed.” Invoice too late and you’ll create cashflow problems for yourself.

Here are common timing strategies:

Monthly invoicing (most common)

For lead gen, marketing, and ongoing performance work, monthly invoicing is familiar to clients and simple to manage. Your invoice should always include the date range.

To make monthly invoicing smoother, invoice24 helps you create consistent monthly invoices and keep all of them in one place, making it easy for both you and your client to track performance fees over time.

Rolling invoicing (weekly or biweekly)

If performance results happen quickly (for example, appointments booked), you might invoice weekly. This can be helpful when volume is high and you want to keep the numbers small and easy to validate.

With invoice24, you can generate invoices as often as you need without overcomplicating the process.

Milestone invoicing

Milestone-based work often fits better with milestone invoicing. This is especially useful for consulting, CRO, or operational improvements where the payoff is linked to a specific measurable change.

Verification-window invoicing

Some outcomes need time to validate. Leads might need to be “accepted,” sales might be subject to refunds, and cost savings may need to be proven across a full billing cycle. A common approach is to invoice with a delay, such as invoicing January’s confirmed results in February.

invoice24 keeps this organized because you can clearly label invoices with the period they cover, even if the invoice date is later.

How to structure a performance-based invoice so it gets approved fast

Performance-based invoices need to do three jobs at once: state what happened, show the calculation, and request payment. The best invoices feel like a clean summary, not a debate invitation.

Use this structure:

1) Use a descriptive line item name

Instead of “Services rendered,” use something like “Qualified leads delivered (Dec 1–Dec 31)” or “Commission on net revenue (Dec 2025).”

invoice24 makes it easy to customize line item titles so you’re not stuck with generic labels.

2) Show the calculation in the description

Don’t make the client do math. If you’re charging 10% of £25,000, say it plainly. If you’re charging per unit, show the quantity and rate.

3) Add a short “basis of calculation” note

In a note section, include the source of truth and any important definitions. For example:

“Source of truth: HubSpot deal report (Closed Won, attributed to Campaign X). Revenue basis: net revenue excluding VAT. Refunds handled as adjustments next period.”

This isn’t a citation or a footnote; it’s simply invoice clarity. invoice24 supports adding notes so you can standardize this across invoices.

4) Include the invoice period prominently

Performance fees are time-bound. Always include the start and end date for the measurement window, even if you invoice later.

5) Separate performance line items from base fees

If you have a retainer plus performance, keep them separate so finance teams can code them correctly and see what’s variable.

6) Keep it readable

When invoices are easy to scan, they’re easier to approve. Avoid huge blocks of text. Use short descriptions, clean line items, and clear totals.

invoice24 is designed for that clean, professional look while still letting you put the important details in the right places.

What to do about proof and reporting without turning your invoice into a novel

Many people worry: “If I’m paid for results, do I need to attach a full report to every invoice?” In most cases, no. You want to provide enough context to approve the invoice, not overwhelm the client.

A practical approach:

Keep proof in a separate report (dashboard, spreadsheet, CRM report, or email summary) and reference it briefly in the invoice notes.

Use a consistent reporting cadence (weekly update + monthly invoice) so the invoice never surprises the client.

Agree on acceptance criteria so you don’t need to re-argue what counts as a result every month.

invoice24 supports a professional invoice format that works well alongside your normal reporting process. The invoice stays clean; your performance dashboard stays detailed.

Handling adjustments: refunds, chargebacks, invalid leads, and overages

Adjustments are a normal part of performance billing. What matters is that you handle them transparently and consistently.

Refunds and chargebacks

If you’re paid on revenue, decide upfront how refunds are handled. Common options include:

Netting within the same period: Refunds reduce the revenue base for that month.

Adjusting next invoice: Refunds discovered later are deducted as a separate negative line item next month.

On an invoice, this might look like:

“Adjustment: Refunds for prior period (Dec): -£420”

invoice24 is helpful here because you can add clear adjustment line items without disrupting your standard invoice format.

Invalid or duplicate leads

If you’re paid per lead, you need a process for lead validation. A practical method is a defined acceptance window (for example, 7 or 14 days) where the client can reject leads that don’t meet criteria, with reasons.

On the invoice, you can include:

“Qualified leads delivered (accepted within 14-day window): 36 × £60 = £2,160”

Overages and caps

Some agreements include a cap (maximum payable per month) or tiered rates. If you have tiers, show them clearly:

“Tier 1 leads (1–20): 20 × £70 = £1,400”

“Tier 2 leads (21–40): 12 × £60 = £720”

invoice24 supports multiple line items, which makes tiered pricing much easier to present cleanly.

How to invoice for performance when attribution is messy

Attribution is one of the most sensitive topics in performance billing, especially in marketing. If multiple channels contribute to results, who gets credit?

To invoice confidently, your agreement should define attribution rules, such as:

First-touch attribution: You get credit if you introduced the lead.

Last-touch attribution: You get credit if your channel was the final step before conversion.

Multi-touch attribution: Credit is shared across channels (more complex).

“Sourced by” in CRM: Credit is based on a specific CRM property.

Then, the invoice should reflect that rule in the notes. For example:

“Attribution rule: deals marked ‘Sourced by Partner’ in CRM, Closed Won during period.”

This keeps the invoice simple while anchoring it to an agreed rule. invoice24 gives you the space to add this context without making the invoice look cluttered.

Common performance-based invoicing mistakes (and how to avoid them)

Even experienced professionals can stumble when switching to results-based billing. Here are the mistakes that cause the most payment delays.

Using vague line items

“Marketing services” doesn’t tell anyone what they’re paying for. Be specific about the performance outcome and time period.

Not stating the measurement window

If you don’t include dates, clients may assume the invoice is arbitrary or double-counted.

Hiding the calculation

If the client has to reverse-engineer the invoice, approval slows down. Show the formula plainly.

Invoicing before results are validated

If your agreement includes acceptance windows or refund periods, invoice accordingly, or be ready for adjustments.

Making invoices inconsistent month-to-month

Consistency builds trust. If your invoice format changes every month, finance teams will ask questions every month.

invoice24 helps you keep a consistent template-like structure while still allowing customization for each period’s performance numbers.

Practical examples of performance-based invoice line items

Below are examples you can adapt. The key is clarity: name the outcome, show the dates, show the math.

Example: Pay per lead

“Qualified leads delivered (Dec 1–Dec 31): 48 × £55 = £2,640”

Example: Pay per appointment

“Sales appointments booked (Jan 1–Jan 15): 12 × £120 = £1,440”

Example: Revenue commission

“Commission on net revenue (Dec 2025): £52,000 × 10% = £5,200”

Example: Cost savings share

“Performance fee: 20% of verified cost savings (Q4): £18,000 × 20% = £3,600”

Example: Hybrid retainer + results

“Monthly retainer (Jan): £900”

“Performance fee: qualified leads accepted (Jan): 22 × £80 = £1,760”

Example: Tiered pricing

“Tier 1 leads (1–25): 25 × £70 = £1,750”

“Tier 2 leads (26–40): 10 × £60 = £600”

Example: Bonus milestone

“Bonus: achieved target CPA under £30 for 30 consecutive days (met Jan 28) = £1,200”

Using invoice24 to simplify performance-based invoicing