How much do ISO agents make in the UK?
ISO agent earnings in the UK are a residual income story, not a salary story — and the honest answer to 'how much do they make?' depends entirely on how long the agent has been building the portfolio, the sourcing channel mix and the retention discipline. This guide walks through the per-merchant maths and the realistic Year 1, Year 3 and Year 5 income curves, with the variables that decide where on the curve you actually land.
The per-merchant maths in plain numbers
A typical UK SME merchant processes between £20,000 and £80,000 of card payments per month, depending on the trade. A cafe might process £15-25k, a busy restaurant £40-80k, a small retailer £20-50k, a service business often less than £10k.
The acquirer's margin on that processing — the bit the ISO earns a residual share of — is typically 20-40 basis points (0.20%-0.40%) on top of interchange and scheme fees. On a £30,000/month merchant at 0.30% margin, that's £90/month of acquirer margin in total.
The ISO's residual share is usually 50-80% of that acquirer margin, depending on the agreement. On the £30k merchant above, a 70% residual share works out to £63/month of residual income — or about £750 per year per merchant.
Multiply that across 100 live merchants and the residual income is around £75,000/year, gross, in perpetuity (less attrition). Across 200 merchants it's £150k. The maths is unspectacular per merchant and spectacular at scale — which is exactly why retention matters more than sourcing.
Year 1 — the build year
A full-time UK ISO agent sourcing actively can typically sign 30-60 merchants in their first year. Not all of those will be live by year-end (acquirer underwriting takes time), and most will have only been processing for part of the year, so the actual paid residual income in Year 1 is far below what the final book size implies.
Realistic Year 1 take-home for a hard-working full-time agent starting from scratch is typically £8,000 to £20,000 of residual income, often topped up by upfront acquirer bonuses or signing payments where the master ISO offers them.
Year 1 is the painful year. The book is small, the cash flow is light, and the attrition on the early-stage merchants disproportionately hurts. Agents who don't have 12-18 months of personal runway usually struggle here.
Year 3 — the compounding starts
An agent who consistently signs 30-60 merchants per year and retains well (under 15% annualised attrition) typically has 90-150 live merchants by end of Year 3.
At 90 live merchants the residual income is typically £55-75k/year. At 150 merchants it's £90-130k/year. The exact number depends on the merchant mix (higher-volume merchants pay more residual per head) and the residual share negotiated with the acquirer.
Year 3 is the year the income usually crosses the level of a strong PAYE salary in adjacent industries — and the year sub-agenting starts to make sense, because the personal book is large enough to anchor the retention motion while the sub-agent focuses on sourcing.
Year 5 — the leverage year
By Year 5, an agent who has consistently sourced, retained and started running one or two sub-agents typically has 200-400+ live merchants across the programme. Residual income at this level is typically £150k-£300k+/year for the owner, depending on sub-agent split economics.
This is where the ISO model pays out — and where the gap between agents who treated retention seriously and agents who didn't becomes obvious. An agent with 300 live merchants at 10% attrition is in a very different position from an agent with 300 ever-signed merchants at 25% attrition, even if the gross sourcing numbers were identical.
Above Year 5 the curve continues, but more slowly: the book gets harder to scale linearly, the sub-agent structure becomes the dominant lever, and the smartest agents start thinking about portfolio sales (residuals trade in the UK at multiples between 18x and 32x monthly income, depending on quality).
The variables that move you up or down the curve
Three variables dominate the earnings curve more than anything else: residual share with the acquirer, attrition rate on the book, and merchant mix.
Residual share is the percentage of acquirer margin you keep. New sub-ISOs often start at 50%; experienced agents on direct ISO agreements typically negotiate 70-80%. A 60% vs 80% share is the difference between £45k and £60k residual income at the same 100 live merchants.
Attrition rate is the percentage of merchants who leave each year. The difference between 10% and 25% attrition compounds dramatically — a book at 25% attrition needs to source 25 merchants a year just to stand still on 100 live merchants.
Merchant mix is the average processing volume per merchant. A book heavy on restaurants and retailers earns substantially more residual per merchant than a book heavy on service businesses or small online sellers. Targeting matters.
The other variable worth naming is sub-agent structure. A single owner with one effective sub-agent on a 50/50 split typically grows the book 60-80% faster than the owner alone — without changing the owner's per-merchant work, because the sub-agent absorbs the sourcing motion.
What ruins the curve
Three things consistently ruin otherwise-promising ISO careers: stopping the sourcing motion too early, ignoring retention until the attrition is already double-digit, and signing the wrong sub-agent agreement early.
Stopping sourcing too early is the most common failure. An agent who hits £40k of residual income at Year 2 and shifts to part-time sourcing usually finds the book has plateaued by Year 3 — because the attrition is now eating the new sourcing, and the leverage point has been missed.
Ignoring retention is the second. A book at 22% attrition is bleeding badly enough to feel it but rarely badly enough to panic, and most agents keep sourcing harder rather than fixing the leak. The retention motion described in the guide to growing an ISO portfolio is the highest-leverage fix.
Signing the wrong sub-agent agreement early is the third — and the most expensive to unwind. The first sub-agent's economics set the precedent for everyone who follows, and a 50/50 split given away on weak terms is almost impossible to renegotiate without losing the agent. Get the structure right before the first signature.
Tooling that supports the curve
Every ISO agent who grows past 100 live merchants eventually invests in a portfolio management system — because the residual reconciliation alone becomes a several-thousand-pound-per-month leak when done in a spreadsheet. ISO portfolio management software covers the system side; residual income tracking software covers the reconciliation specifically.
The single biggest impact on earnings, though, is not the tooling. It's the discipline to keep sourcing, keep retaining and keep structuring the sub-agent layer cleanly — and the patience to let the maths compound over Years 1-5.
Frequently asked questions
How much does an average UK ISO agent make per year?
There's no single 'average' — earnings depend entirely on how long the agent has been building the book. Realistic Year 1 income from scratch is £8-20k of residual; Year 3 is typically £55-130k for a steady-state full-time agent; Year 5 with one or two sub-agents is typically £150-300k+. The number that matters is the trajectory, not any single year.
How much does an ISO agent earn per merchant per month?
Typical UK SME merchant residual income per month is £30-100 for the ISO, depending on processing volume, acquirer margin and the ISO's residual share. A £30,000/month merchant at 0.30% acquirer margin and a 70% residual share pays the ISO about £63/month, or roughly £750/year.
Is being a UK ISO agent worth it?
Financially, yes — if the agent commits to a 3-5 year build, stays disciplined on retention, and structures sub-agent economics carefully. The model rewards patience and operational consistency more than it rewards short-term hustle. Agents looking for high Year 1 income usually find ISO work disappointing.
How do I get a higher residual share from my acquirer?
Residual share is negotiated on the basis of book size, retention quality, payment volume contributed and the level of service the ISO provides post-live. Agents with 100+ live merchants, sub-15% attrition and a track record of supporting the merchant directly typically have leverage to move from a starting 50% share towards 70-80%.