MDR for Interior Designers: Card Acceptance Costs Explained

Published: 27 October 2026

Category: how-to-guides | cardbuzz

Tags: interior design, MDR, card acceptance, merchant fees, payment terminals, design studio payments, interior business costs

A homeowner paying by card for a modular kitchen, a full-home interior, or a single room makeover rarely thinks about what happens after the payment is approved. For the interior design studio, though, that payment sets off a chain of charges, settlements, and reconciliations that quietly shapes the margin on every project. The merchant discount rate, commonly shortened to MDR, is the fee a business pays for accepting a card payment. It is not usually one simple charge. It is a bundle of interchange paid to the cardholder's bank, assessments paid to the card network, and the acquirer's own margin for providing the terminal, the connection, and the settlement service.

MDR is manageable once it is understood. This guide explains the mechanics in plain terms, so a studio can have a better conversation with an acquirer.

What MDR Actually Contains

MDR is best thought of as layers. The first layer is interchange, which goes to the bank that issued the customer's card. It compensates that bank for funding the transaction, for the interest-free period the cardholder enjoys, and for fraud and credit risk. Interchange varies by card type: a basic debit card, a premium credit card, and a commercial card do not carry the same cost, and the studio usually cannot see this split on the customer receipt.

The second layer is the scheme fee paid to the card network for routing, authorisation, and clearing. The third layer is the acquirer's margin, which covers terminal hardware or rental, software, support, and chargeback handling. When an acquirer quotes a blended rate, all the layers are folded into one figure. When it quotes an interchange-plus arrangement, the layers are shown separately. The blended model is simpler to budget, while the interchange-plus model is more transparent about what changes when a client pays with a costlier card.

Why Interior Projects Cost What They Do to Accept

Interior design transactions differ from many other service transactions in ways that matter to cost. The ticket size varies enormously across projects. A single room refresh or a furniture package is a modest sale, while a full-home interior with carpentry, modular units, lighting, and soft furnishings is a large one, so the absolute fee per transaction varies just as much even when the rate looks steady. Premium cards are common for larger projects, because clients furnishing a whole home often hold reward cards and choose to pay by card precisely to earn benefits. Those cards carry higher interchange, which the studio absorbs.

Staged payments add another wrinkle. A project paid in an advance, progress instalments, and a final balance generates several card transactions rather than one, each carrying its own fee. A studio should therefore think about acceptance cost on the whole project, not on any single payment.

Blended Rates Versus Interchange-Plus

A blended rate gives the business one predictable figure for most card transactions, which makes budgeting straightforward. Its drawback is opacity: when a statement shows a higher effective rate than expected, it is hard to tell why.

An interchange-plus arrangement separates the pass-through costs from the acquirer's margin, so the business can see how much of each project went to interchange and scheme fees. The trade-off is variability: the effective rate moves with the card mix, so a month heavy in premium credit cards will cost more than a month heavy in debit cards. Whichever model is chosen, the business should ask what is excluded: terminal rental, statement fees, minimum monthly charges, chargeback administration fees, and settlement charges can all sit outside the headline rate.

Reading the Monthly Statement

The monthly statement is where MDR stops being abstract. An interior studio should reconcile it in a few steps. First, check that the gross card sales on the statement match the terminal's own totals for the month. Second, divide the total fees by gross sales to find the effective rate, and compare it with the quoted rate; a persistent gap is a question to put to the acquirer, not a rounding difference to ignore. Third, look for fees beyond MDR, such as rentals, minimums, and chargeback charges, and ask whether each one was disclosed at sign-up. Fourth, check the settlement timing: funds that arrive several working days after the sale create a working-capital cost of their own, particularly for a studio that orders materials and pays carpenters on short credit.

Negotiating and Reducing the Cost

Reducing MDR starts with information, not with haggling. A studio that can show its monthly volume, its average ticket, and its card mix is in a stronger position than a studio that simply asks for a lower figure. Volume commitments and consolidated terminals across design teams can be negotiating points, but each should be weighed against flexibility: a long lock-in that prevents switching may cost more over time than a slightly higher rate with freedom to move.

The honest approach is to price acceptance cost into project quotes from the start, so no single payment method breaks the margin.

Closing Thoughts

MDR is the price of serving clients who arrive without cash and approve large home projects with confidence. Understanding its layers and reviewing the arrangement regularly keeps that price fair.