An independent sales organization, or ISO, sells and services card acceptance on behalf of an acquiring bank without holding scheme membership or ever touching merchant funds. The bank underwrites the merchant, holds the account and carries the risk; the ISO brings the merchant in and keeps the relationship afterwards.
Registered ISO or unregistered agent
An ISO registered with Visa and Mastercard through its sponsoring acquirer may use its own brand in front of merchants, price within agreed bands and appear on merchant paperwork. An unregistered agent sells under the acquirer's name with far less freedom.
Registration costs money and annual scheme fees, which is why smaller sales operations stay agents. For the merchant the practical consequence is identical either way: the contract is with the bank, and the bank can end it.
Residuals are the actual product
ISOs are paid mainly in residuals, a share of the processing margin on every merchant they placed, paid monthly for as long as that merchant keeps processing. Signing bonuses per account and margin on terminals add to it, but residual income is the business.
That compensation shape predicts ISO behavior better than any sales strategy. Attrition is the enemy, because a merchant that leaves takes its residual with it, so service quality and defending existing pricing matter more than the count of new signings.
Why residual portfolios change hands
A book of residuals is contracted, reasonably predictable cash flow, so it is bought and sold like any other income-producing asset, typically at a multiple of monthly residual adjusted for attrition, merchant concentration and the terms of the agreement with the sponsoring bank.
Buyers look at the same things every time: whether the portfolio survives a change of sponsor, whether residuals continue if the ISO itself is sold, and how much of the income depends on a handful of large merchants. Those clauses usually matter more than the headline multiple.
The line an ISO does not cross
Funds never pass through the ISO, and the independent sales organization definition turns on that limit: sales and service, never money. Settlement runs from the acquiring bank to the merchant's own account, so the ISO cannot change payout timing, cannot hold a balance and does not fund chargebacks. A payment facilitator sits on the other side of that line, holding a master account and taking on both the underwriting and the losses, while a payment service provider sells a bundled product of its own rather than someone else's acquiring.
Merchants signing through an ISO should confirm which bank holds the merchant account and read the settlement terms there, since the ISO can neither change them nor release a frozen balance.