Interchange-Plus Pricing for California Merchants, Explained

Interchange plus pricing in California is the model most experienced merchants end up on once they get tired of guessing what a "2.9% plus 30 cents" flat rate is actually hiding. The idea is simple: the wholesale cost set by Visa, Mastercard, Discover and the issuing banks gets passed through at cost, and your processor adds a fixed markup on top. This guide explains each layer, shows you how to read one, and covers the California rules that decide what you can do with the cost once you understand it.

The three layers of every card transaction

When a customer in Fresno taps a card at your counter, the fee you pay has three parts.

1. Interchange. Paid to the bank that issued the card. Set by the card networks in published tables, not by your processor. Varies by card type (debit vs. credit vs. premium rewards vs. commercial), how the card was presented (chip, tap, keyed, online), and your industry.
2. Assessments and network fees. Paid to Visa, Mastercard and the other networks themselves. Small percentages plus per-item fees, also published.
3. Processor markup. What your processor keeps. Quoted as a percentage plus a per-transaction amount, for example 0.20% + $0.10.

Interchange-plus means layers one and two are passed through at exactly what they cost, and layer three is the only number you negotiate. This is what a pass-through pricing arrangement is designed to do.

Why the wholesale part moves around so much

A regulated debit card (from a bank over $10 billion in assets) has interchange capped by federal rule at roughly 0.05% plus $0.21 plus a small fraud adjustment. A premium travel rewards credit card keyed in over the phone can run above 3%. Same processor, same merchant, wildly different cost, because the issuer and entry method changed.

That variance is why flat-rate pricing exists. The flat-rate processor averages everything and charges you the blended number, which means the taqueria taking mostly debit is subsidizing the online boutique taking rewards cards. If your customer mix skews debit or in-person, interchange-plus almost always wins. If it skews keyed premium credit, the gap shrinks.

A few things you control that lower the wholesale part: taking chip or tap instead of keying, passing address verification on card-not-present sales, settling batches daily, and sending Level 2 and Level 3 data on business-to-business transactions (tax amount, invoice number, line items). B2B suppliers in the Inland Empire logistics corridor leave real money on the table by skipping Level 3.

Reading an interchange-plus statement

A real interchange-plus statement is longer than a flat-rate statement, and that is the point. You should see:

• Each interchange category your transactions hit, with volume, count and the rate for each.
• Network assessments listed separately.
• Your processor's markup as its own line, matching the quote you were given.
• Any monthly or per-item fees (gateway, PCI, statement) listed by name.

If the statement shows a single blended "discount rate" with no interchange detail, you are not on true interchange-plus, whatever the sales rep called it. Also check for "padding" on the pass-through lines: some processors quote interchange-plus and then quietly add basis points to interchange itself. Compare the rate on a common category, say Visa CPS/Retail debit, to the published Visa table.

Interchange-plus versus tiered versus flat

Tiered pricing sorts transactions into "qualified," "mid-qualified" and "non-qualified" buckets, and the processor decides which bucket each one lands in. It is the least transparent model and the one where a good-looking headline rate turns into a bad effective rate. Flat-rate is transparent but expensive for low-cost cards. Interchange-plus is transparent and cost-based, at the price of a more complicated statement.

For a Whittier retail shop doing $30,000 a month, the difference between a fair interchange-plus deal and a flat 2.9% can be several hundred dollars monthly. We ran through the math in How Much Does Credit Card Processing Cost in Whittier?, and the mechanics apply anywhere in the state.

The California layer: SB 478, surcharges and disclosure

Once you know your true card cost, the natural next question is whether you can pass it to customers. California is more constrained than most states.

SB 478, effective July 2024, requires that advertised or displayed prices include all mandatory fees. The Attorney General's guidance addressed how card fees and surcharges interact with that requirement, and the practical takeaway for most merchants is that a surprise "card fee" added at checkout is a problem. Cash discounts (posting the card price and offering a lower cash price) are handled differently from surcharges, and restaurant service charges got their own follow-up legislation. Check the current rule and confirm with counsel before implementing any of it; the guidance has been refined more than once, and getting it wrong is a consumer-protection exposure, not just a card-network one.

Card-network rules add their own layer: surcharges are capped, can only apply to credit (never debit), must be disclosed at the entrance and point of sale, and require advance notice to your acquirer. Debit cannot be surcharged anywhere in the country.

When interchange-plus is not the right fit

Very small merchants doing under a few thousand dollars a month sometimes do better on flat-rate because monthly fees on an interchange-plus account outweigh the savings. High-risk merchants often cannot get true interchange-plus at all in year one; the acquirer prices in the risk with a higher markup or a rolling reserve, and moves you toward cost-plus once you have a clean history. And a business that takes mostly premium rewards cards keyed online sees less of a gap.

The honest answer for most California merchants over roughly $10,000 a month in card volume is that interchange-plus with a clearly disclosed markup is the fair deal, and the work is in reading the statement well enough to confirm you are actually getting it.