A residual split is your percentage of the residual pool. A buy rate is the wholesale floor that creates that pool. Compare the dollars, not the headline. A 70 percent split of a thin pool, after a fat buy rate, can pay less every month than a 50 percent split of true cost-plus. The only honest comparison is the waterfall: sell rate minus buy rate minus every line the house keeps before the split. Demand that math on a real statement, in writing, before you sign.
This is the arithmetic companion to how ISO residuals work. That piece covers vesting, portability, and successor protection. This one is why the percentage on the recruiting one-pager is not the offer.
Split, buy rate, and sell rate
Three numbers, in that order.
Sell rate. What the merchant is billed: the percent, the per-item, and the monthly extras. This is the top of the stack. It is not your residual.
Buy rate. What your ISO, sponsor, or residual desk charges the book for that volume. It is not interchange. It is not the merchant's rate. It is a wholesale price. If it sits above true cost (interchange plus assessments plus the processor's actual cost), the gap is a pre-split skim. The house keeps that gap at 100 percent. You never see it in the split.
Split. Your contractual percentage of whatever remains after the buy rate, and after any other deductions the agreement names. Seventy percent of a $250 pool is $175. Fifty percent of a $500 pool is $250. Same merchant. Same volume. Different check.
People compare 70 to 50 because those are the numbers on the flyer. The flyer omits the denominator.
Residual dollars = (sell minus buy minus excluded lines) × split.
Raise the buy rate and you shrink the parentheses. Raise the split and you only multiply what is left. A fat buy rate is more powerful than a fat split because it hits before the multiply.
You also do not split interchange. U.S. banks collected nearly $66 billion in interchange ("swipe") fees in 2025, up from $64 billion in 2024 (Federal Reserve Bank of St. Louis, 9 Apr 2026). That money goes to issuing banks. Network assessments go to the brands. Your residual is carved from markup only. If a recruiter talks as if you "share the rate," ask whether they mean the merchant's billed rate or the markup. Those are different piles.
Worked example: $100,000 a month (illustrative)
All figures in this section are illustrative. They are not a quote, not a book average, and not a promise.
Merchant volume: $100,000 billed at 2.70 percent ($2,700). True cost (interchange plus assessments plus disclosed processor cost): 2.20 percent ($2,200). True margin: 50 BPS ($500). One basis point is 0.01 percent.
Offer A sets the buy at 2.45 percent. The house takes 25 BPS ($250) at 100 percent before the split. The remaining pool is $250. A 70 percent split pays you $175 this month ($2,100 annualized if volume holds). The house keeps $325.
Offer B sets the buy at the disclosed 2.20 percent cost. The pool is the full $500. A 50 percent split pays you $250 this month ($3,000 annualized). The house keeps $250.
Same merchant, same sell rate. The "worse" split pays $75 more per month, $900 more per year, on one account.
| Item | Offer A (70% / fat buy) | Offer B (50% / cost-plus) |
|---|---|---|
| Merchant billed | 2.70% ($2,700) | 2.70% ($2,700) |
| Buy rate | 2.45% ($2,450) | 2.20% ($2,200) |
| Residual pool | $250 (25 BPS) | $500 (50 BPS) |
| Headline split | 70% | 50% |
| Your residual | $175 / month | $250 / month |
| Annualized, volume held | $2,100 | $3,000 |
- Buy rate 2.45% on $100,000 volume
- Pool after buy: 25 BPS = $250
- Your residual: $175/month ($2,100/year)
- Buy rate equals disclosed cost of 2.20%
- Pool after buy: 50 BPS = $500
- Your residual: $250/month ($3,000/year)
If you only remember one line: 17.5 BPS in your pocket versus 25 BPS in your pocket. That is what 70 percent of 25 BPS and 50 percent of 50 BPS actually are.
What comes out before the split
The buy rate is the biggest lever. It is not the only one. A waterfall is the ordered list of deductions between the merchant's billed fees and the number your split multiplies. Ask for it as a formula, not a speech.
Common deductions that never hit your split, or hit it after the house has taken them:
- Inflated buy rate. Covered above. The silent 100-percent commission to the desk.
- Pass-through that is not passed through. Interchange and assessments should flow at cost on an interchange-plus book. If they are baked into a fat buy, you are not on cost-plus. You are on a bundled wholesale rate with a split sticker.
- Excluded line items. PCI program fees, statement fees, batch fees, gateway, next-day funding, annual "regulatory" charges, and monthly minimums are often 100 percent house. Card volume looks big. Your residual ignores half the invoice.
- Zeroed per-item. Sell $0.10, buy $0.10, item residual is $0. All of your split then rides on the percent, while the house may still have room under a lower true per-item cost. Confirm the schedule. Do not assume the item is in the pool.
- BIN sponsorship, risk reserves, and "net profit" language. If the split is of net after reserves, the reserve is both a timing delay and a haircut. Get the definition of net in writing.
- Volume basis. Split of gross card sales is not split of net deposits after refunds and chargebacks. Confirm the denominator.
None of these is automatically abusive. Some are real costs. The failure is hiding them above the split so the 70 percent still looks like the story.
Mix is the other trap. Debit interchange is usually cheaper than rewards credit. True cost-plus moves when mix moves. A single 2.45 percent buy does not. If the desk will not show buy by card type, or at least debit versus credit, you are taking a mix bet you cannot price.
How to compare two offers on one statement
Take one recent merchant statement. Hold the merchant's billed fees constant. Then force each offer onto the same sheet.
- Rebuild the merchant's current bill. Every processing line, not just the qualified rate. Total fees divided by card volume is the effective rate you are replacing.
- Ask each provider for the buy. By card type if they publish it, or a single buy if that is all they sell, plus the list of lines that sit outside the split.
- Compute the pool. Billed processing margin minus buy minus excluded lines.
- Multiply by the split. That is the monthly check on this account, before attrition.
- Stress mix. Repeat on a debit-heavy month and a rewards-heavy month. A fat blended buy that looks fine on debit will not look the same when premium credit shows up.
Write five numbers down: sell, buy, excluded, split, dollars. If a recruiter will not fill those five, you do not have an offer. You have a headline.
If you want the merchant side of the sheet in as-billed form, run the analyzer and carry that printout into the split conversation.
Cost-plus is a buy-rate claim, not a slogan
"Cost-plus" and "interchange-plus" describe the same idea from two chairs. For the merchant, interchange-plus means they see interchange, assessments, and a published markup. For you, cost-plus means your buy is that cost (or cost plus a small, disclosed desk fee), and your split applies to the markup you actually sold.
A shop can say cost-plus and still sell you a 2.45 percent buy. That is cost-plus in name and a buy-rate program in math. The test is whether you can recompute last month's residual from the statement, the published interchange, the published assessments, and the markup, and land within rounding of the residual report. If you cannot, the waterfall is incomplete.
The pricing model still changes how the pool is expressed. Interchange-plus makes the markup a clean BPS-over-cost number. Tiered and flat-rate bury it. Surcharge and dual pricing move some cost to the cardholder. Neutral advice on the model is part of residual quality: accounts on a model that fits them leak slower.
After the dollars, the rights
A thicker check on a residual you do not own is still a rental. Vesting, portability, and successor protection decide whether this month's $250 is an asset. Do not let a 70 percent banner postpone that read. Get the waterfall and the durability clauses in writing. Partner terms at Relyon are published on the partners page.
Chase the split and you optimize for the recruiting call. Chase dollars on a disclosed buy, on residuals you vest, and you can actually model a book.
FAQ
What is a buy rate in merchant services? A buy rate is the wholesale price your ISO or residual desk charges the book for a merchant's volume. It sits under the merchant's sell rate. Your residual is a split of what remains after that buy and after any other deductions the contract names.
What is a residual split? The split is your contractual percentage of the residual pool. It is not a percentage of the merchant's billed rate and not a percentage of interchange. Confirm in writing what the pool includes and what it excludes.
Can a 50 percent split pay more than a 70 percent split? Yes. If the 70 percent offer uses a fat buy rate, the pool is smaller before anyone multiplies. In the illustrative $100,000 example in this article, 70 percent of 25 BPS pays $175 a month and 50 percent of 50 BPS pays $250.
What is a residual waterfall? The waterfall is the ordered list of deductions between the merchant's billed fees and the number your split multiplies. Buy-rate inflation, excluded monthly fees, zeroed per-item charges, BIN costs, and reserves all live here. If you cannot recompute last month's residual from that list, you do not have an offer.
Does my residual split include interchange? No. Interchange is paid to the issuing bank. U.S. banks collected nearly $66 billion in interchange fees in 2025 (Federal Reserve Bank of St. Louis, 9 Apr 2026). Your split applies to markup above cost, not to that issuer revenue.
How do I compare two ISO residual offers? Hold one merchant statement constant. Write down sell, buy, excluded lines, split, and dollars for each offer. The higher headline split is not automatically the higher check. Then read vesting, portability, and successor protection so the dollars are actually yours.
Sources
- Federal Reserve Bank of St. Louis, "Banking Analytics: Credit and Debit Card Fees Collected by Banks Rose in 2025," 9 Apr 2026. https://www.stlouisfed.org/on-the-economy/2026/apr/banking-analytics-credit-debit-card-fees-collected-banks-rose-2025
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