The Billing Layer Nobody Talks About
Accounts payable automation has long been a grubby, unglamorous corner of fintech – the kind of infrastructure problem that enterprise software vendors have been charging enormous licensing fees to “solve” for decades, without ever quite solving it. The workflows are messy, the data is fragmented, and the compliance requirements shift by industry. Most startups building financial products simply bolt on whatever payment rails they can get access to and move on. Mercoa is betting that approach leaves a wide-open gap at the infrastructure layer.
The San Francisco-based startup has built what it describes as an embeddable AP and billing infrastructure API – the kind of tool that lets a software platform add vendor payments, invoice management, approval workflows, and ACH or check disbursement to their product without rebuilding those systems from scratch. It is not a product end users log into. It is the layer that powers the AP features inside someone else’s platform.
That distinction matters enormously.
Where Stripe Falls Short
Stripe is the obvious reference point for any API-first payments company, and Mercoa has leaned into that comparison deliberately. Stripe built the gold standard for collecting money – card processing, subscription billing, marketplace payouts. But collecting money and disbursing money to business vendors are structurally different problems. Vendor payments involve tax compliance (1099 filing, W-9 collection), multi-step approval routing, invoice OCR, and payment method flexibility across ACH, check, and wire. Stripe’s existing suite does not handle all of that natively, and the workarounds required to build it on top of Stripe can take an engineering team months.
That friction is exactly the surface area Mercoa targets. A vertical SaaS company serving property managers, healthcare groups, or logistics operators often needs to let their customers pay vendors directly inside the platform. Building that from scratch means building a mini-bank product: KYC flows, vendor onboarding, payment scheduling, and reconciliation. Mercoa packages all of that behind a single API and a set of white-label UI components that can be dropped into a product in days rather than quarters. The commercial model runs on transaction fees, which aligns Mercoa’s revenue with the platform’s growth rather than upfront licensing.
The approach echoes what has worked in adjacent API infrastructure categories. Resend’s developer email API has pulled a similar move against SendGrid – find the place where legacy vendors impose the most friction on developers, strip it out, and charge on usage. Mercoa is applying that same logic to a financial workflow that is simultaneously more complex and more lucrative than email delivery.
The Embedded Finance Angle Nobody Is Chasing Hard Enough
The broader embedded finance space has attracted enormous attention, but most of it has concentrated on the consumer side – embedded lending, buy-now-pay-later, branded debit cards. Business-to-business payment infrastructure for software platforms has attracted far less capital and far less press, which is part of why Mercoa’s positioning is working. The competitive field is thin. Legacy AP automation vendors like Bill.com and Tipalti are built as end-user products, not as infrastructure layers. Integrating them into a third-party platform requires custom API work that many vendors do not officially support or actively discourage.
Mercoa’s entire architecture assumes it will never be the product the end user sees. That design decision shapes everything: the API surface, the white-label UI components, the onboarding flows, the compliance layer. A property management platform can launch a “pay your vendors” feature with Mercoa under the hood, and their customers will never know Mercoa exists. That invisibility is not a weakness – it is the core value proposition. Platforms do not want their users leaving to a third-party dashboard to run payables. They want the workflow embedded in the product their users already live in.
The compliance angle deserves particular attention. 1099 filing season is a nightmare for any platform that routes payments to contractors or vendors. The requirement to collect tax information, validate it, and file correctly with the IRS is a legal obligation that many platforms have historically fumbled, relying on clunky manual processes or expensive accounting workarounds. Mercoa handles vendor tax documentation as part of the onboarding flow, which reduces that liability for the platform and removes a significant barrier to building payment features at all.
A Market That Earns Its Complexity
B2B payments are a volume and margin story. Business payments move through ACH and wire rather than credit card rails, which keeps per-transaction costs lower, but the transaction sizes are orders of magnitude larger than consumer payments. A single vendor invoice for a commercial real estate operator can run into six figures. Platforms that route those payments earn basis points on real money – and Mercoa, sitting in the middle of that flow, earns alongside them. The math on embeddable AP infrastructure is better than it looks from the outside, which is precisely why the category will not stay quiet much longer.
Stripe will not ignore this gap indefinitely – it has the engineering depth and the distribution to build or acquire its way into deeper AP functionality. But for now, Mercoa is onboarding the vertical SaaS companies that Stripe’s existing product does not quite fit, and those relationships tend to be sticky. A platform that rebuilds its entire vendor payment workflow on Mercoa’s infrastructure does not migrate that off casually.
