How to calculate ISO residuals, with a worked example

Every month, each processor sends an ISO a residual report: one line per merchant, showing what that merchant earned. Turning that report into what each agent is owed is a chain of five steps. None of them is hard. What makes month-end painful is that every step has a percentage, every percentage has a base, and the base is where offices disagree with their agents, and sometimes with their own spreadsheet.

This guide walks through the chain once, on one merchant, with every number shown.

The five steps

Steps 1 and 2 are generally done by the payment processor. You will rarely calculate them yourself. A residual file usually already breaks out Total Profit for each merchant: what the merchant paid, minus the processor's costs. That is the number your month-end starts from. It is still worth understanding how it is built, because it is the only way to check that your Schedule A is being applied correctly.

Step 3 depends on the report. Some processors report Total Profit and leave the split to you. Others send a file that is already net of their share. Know which one you are holding before you apply any percentage. Steps 4 and 5 are always yours, every month.

A worked example

One merchant, one month: $50,000 in card volume across 800 transactions, priced at interchange plus 0.40% and $0.10 per transaction, with a $10 monthly fee.

Steps 1 and 2 below show how the processor arrives at Total Profit. In practice you read the result off the residual file.

Step 1. Merchant markup. Interchange and assessments pass through to the card brands and issuing banks, so they never reach the ISO. The markup is what is left:

• 0.40% × $50,000 = $200.00
• $0.10 × 800 transactions = $80.00
• Monthly fee = $10.00
• Markup: $290.00

Step 2. Processor costs (Schedule A). Your buy rates. In this example: 5 basis points on volume, $0.04 per transaction and a $5 monthly account cost.

• 0.05% × $50,000 = $25.00
• $0.04 × 800 = $32.00
• Monthly cost = $5.00
• Costs: $62.00. Total Profit on the merchant: $290.00 − $62.00 = $228.00

This $228.00 is the figure you would normally find on the residual file.

Step 3. Processor split. The ISO agreement in this example pays the ISO 80% of Total Profit.

• 80% × $228.00 = $182.40 to the ISO

Step 4. ISO deductions. The office charges a $10 gateway fee against this merchant before anyone is paid.

• $182.40 − $10.00 = $172.40 remaining

Step 5. Agent split and override. The agent is on a 50% split. Their manager earns a 10% override on the agent's commission.

That is the whole calculation for one merchant. A real month is the same thing a few hundred or a few thousand times, across several processors whose reports do not look alike.

Which number does the agent's split apply to?

This is the question behind most residual disputes. "50%" means nothing until both sides agree on 50% of what. Using the example above, the same 50% agent could be owed three different amounts:

All three are in use across the industry. You can try your own numbers on each base in the residual split calculator. The gap between the first and the last is $27.80 a month on a single mid-sized merchant. Across a 200-merchant book that is a serious amount of money resting on one sentence in an agreement. Write the base into every agent agreement in plain words, and make sure your calculation uses the same one.

How do overrides and sub-agent splits change the math?

An override pays an upline (a manager, a master agent, or the person who recruited the agent) on business they did not sell themselves. There are two common ways to define it, and they do not produce the same number:

• A percentage of the agent's commission. In the example, 10% × $86.20 = $8.62.
• Points on the residual itself. "10 points" on the $172.40 remaining would be $17.24, twice as much.

A shared merchant is different from an override. When two agents close a deal together, each owns a share of the merchant (say 60/40), and each agent's own split applies to their share. The shares on a merchant should never add up to more than 100%. When they do, the house is paying out money it never received, and nothing in a spreadsheet will warn you.

Does the calculation change with tiered or flat-rate pricing?

Only step 1 changes. With tiered or flat-rate pricing, the merchant pays a bundled rate, and the markup is that revenue minus the actual interchange and assessments on the month's transactions. The processor works this out, and the result lands on the residual report as the merchant's income or profit figure. From step 2 onward the chain is identical. This is why a flat-rate merchant's residual moves from month to month even when volume is steady: the card mix changed, so interchange changed.

What goes wrong in practice

These are the errors that show up when the calculation lives in a spreadsheet. Each one below has happened in a real book.

• The wrong month. Some processors send a workbook with a tab per month. Read the wrong tab and every agent is paid on another month's numbers, and the totals still look plausible.
• Counting rows instead of merchants. Some reports repeat a merchant across several rows, one per income type or card brand. In one book, counting rows overstated the merchant count by 30%. Match on merchant ID, never on row.
• Summing a column that should not be summed. When a merchant has several rows, some columns (like monthly volume) repeat on every row. Add them up and volume doubles.
• A deduction with no rate. A fee is set up, the amount is left blank, and it silently deducts nothing for months.
• A rate change with no date. An agent's split changes in June, the spreadsheet is updated in place, and now a re-run of March uses June's rate.
• Reconciling by adding up agent statements. A merchant with an override, or with two agents, appears on more than one statement. Adding statements double-counts it. Reconcile against the processor's report instead.

A short checklist for month-end

1. Confirm each report covers the month you think it does, before anything else.
2. Count unique merchant IDs and compare with last month. A large swing is a data problem until proven otherwise.
3. Tie the total profit you are about to split back to the processor's own total.
4. Check that every merchant has an agent, and that no merchant's shares exceed 100%.
5. After calculating: total paid to agents, plus overrides, plus house, must equal what came in after deductions. If it does not, stop.

Frequently asked questions

What is a residual in merchant services? A residual is the recurring income an ISO or agent earns each month from a merchant's card processing, for as long as that merchant keeps processing. It is a share of the markup the merchant pays above interchange and card brand assessments, after the processor's costs.

What is a Schedule A? Schedule A is the pricing schedule attached to an ISO's or agent's agreement. It lists the buy rates: the basis points, per-transaction costs and monthly fees the processor charges before profit is shared. Every cost in step 2 of the calculation comes from it.

What is a typical agent split? Splits commonly range from about 50% to 80% of the residual, depending on how much the ISO provides (leads, support, equipment, a bonus up front) and on the agent's volume. The percentage matters less than what it applies to, so confirm the base before comparing two offers.

Is an override paid out of the agent's commission? Usually not. In most offices the override is paid by the house on top of the agent's commission, so the agent's pay is unchanged and the house margin is lower. Some agreements do net it out of the agent's side. Your agreements should say which.

How long does calculating residuals take? By hand, offices with a few processors and a dozen agents commonly spend two to three days a month on it. The calculation itself is quick. The time goes into cleaning reports, matching merchants to agents, and checking the result.

Can software do this automatically? Yes. SplitRun reads the residual reports you already receive, matches merchants to agents, applies splits, overrides and deductions in a set order, and produces a statement per agent. The product's own calculation order is documented in How SplitRun calculates commissions, and you can see the output in the sample agent report.