Costs and pricing
Part of What do affiliate marketing costs and pricing look like for a UK brand?
Why affiliate marketing return on investment needs a cost baseline first
A step-by-step method for working out affiliate marketing return on investment in pounds, from commission and platform costs to a clean before-and-after table.
What to take away
- GOV.UK lists a reduced VAT rate of 5% and a zero rate for some goods, so gross and net figures diverge before you count a single commission (VAT rates on different goods and services, GOV.UK).
- Affiliate marketing return on investment is (net revenue minus total programme cost) divided by total programme cost, expressed as a percentage.
- Build the cost side in pounds first: commission, platform fee, tracking, content and staff time.
- Compare like with like, using the same period and the same VAT treatment on both sides.
- Keep the ICO's rules on consent and cookies in view, because non-compliant tracking can wipe out reported revenue overnight.
Why the cost baseline comes before the ratio
Separate gross and net revenue
Start with the money that actually lands. A sale at £100 including VAT is not £100 of revenue if the product carries 20% VAT. GOV.UK sets out the standard rate, the reduced rate and the zero rate, and affiliate programmes often promote a mix of all three. Convert every order to a net figure before you calculate anything.
Label each column with its VAT treatment before you start. For example, a programme generating £50,000 including VAT across mixed-rate products might net £43,000 once the correct rates are applied.
VAT treatment matters most when a programme spans categories. A commission on a zero-rated item is not comparable with the same commission on a standard-rated one, so convert both before you compare periods.
List every cost line
Most teams count commission and stop. That understates the denominator. Include the network or platform fee, tracking setup, creative production, cashback funding and the internal hours spent on reconciliation. A practical costs and budget guide is the right starting point because it separates fixed from variable spend.
For illustration, a team paying £400 a month for platform access plus £6,000 a month in commission carries a £76,800 annual cost base before staff time. Add 0.2 of a full-time equivalent at £35,000 and the denominator grows again.
Cashback and voucher funding is easy to miss because it often lands as a reduction in net revenue rather than a separate invoice. Decide whether it sits in the cost column or nets off the top, and apply the same choice every period.
How to build the calculation
Set the period and the comparison
Choose a period long enough to cover a full purchase cycle. Monthly works for fast-moving retail, quarterly for considered purchases. Then build the before-and-after table below so the movement is visible rather than asserted.
Use like-for-like periods. A five-week trading month compared with a four-week one will move the ratio without anything changing in the programme.
| Measure | Before | After |
|---|---|---|
| Net revenue | £43,000 | £58,000 |
| Commission paid | £4,800 | £7,200 |
| Platform and tracking | £4,800 | £4,800 |
| Content and creative | £1,200 | £2,400 |
| Staff time | £7,000 | £7,000 |
| Total cost | £17,800 | £21,400 |
| Return on investment | 142% | 171% |
All figures are illustrative examples in pounds sterling.
Treat compliance as a cost, not an afterthought
The ICO's guidance on direct marketing and electronic communications covers consent and cookies, and it applies to the tracking that generates your revenue. If a consent gap means you cannot lawfully attribute a sale, that revenue should not sit in the numerator. A budget template helps you hold consent costs alongside commission rather than discovering them mid-quarter. Consent management tooling and audit time belong in the denominator too.
What distorts the number
Attribution and incrementality
Last-click attribution credits the affiliate for sales that may have happened anyway. Where you can, compare a period with the channel running against a matched period without it. Ask whether the sale would have happened without the click before treating the credit as growth. The Federal Trade Commission publishes competition and consumer protection guidance documents, and disclosure and substantiation expectations apply to the promotions your partners run.
Seasonality and payback timing
Commission is paid after the sale, often on a 30 to 60 day cycle, while platform fees leave the account monthly. A ratio calculated on a calendar month can look healthy while cash is still negative. Track cumulative cash position alongside the percentage, and review both at the same point each period. If commission terms change mid-period, split the period rather than averaging two different rate cards.
Common questions
What counts as cost in affiliate marketing return on investment?
Everything you spend to run the channel: commission, platform or network fees, tracking, creative, cashback funding and the internal hours used to manage it. Leaving out staff time is the most common reason a ratio looks better than the bank balance.
Should I use gross or net revenue?
Net. Strip VAT using the correct rate for each product first, because mixed-rate programmes will otherwise overstate both revenue and the return.
How often should the ratio be recalculated?
At least every reporting period, using the same period length each time. Recalculate sooner if commission rates, platform fees or consent arrangements change, since each of those moves the denominator directly.
