Microsoft partners face a major back-end change today as the legacy Microsoft Customer Agreement (MCA) attestation API and its associated UX flow are officially retired on January 5, 2026. Partners that have not adopted the enhanced MCA attestation API will see their sales motion slow down or break, as new customers will now be pushed to accept the MCA directly in the Microsoft 365 admin center before any new orders can be placed.
What is changing for Microsoft partners today
The MCA attestation API underpins how many Cloud Solution Provider (CSP) partners and indirect resellers record that a customer has accepted the Microsoft Customer Agreement as part of their automated onboarding and ordering flows. Instead of sending customers through Microsoft-owned UX every time, partners have been able to embed the relevant terms and capture acceptance via API, then pass that signal back to Microsoft.
With the retirement of the legacy MCA attestation API and UX flow on January 5, 2026, that old path disappears. From today forward, partners are expected to use the enhanced MCA attestation API and its updated contract model, which was designed to be more robust, auditable, and aligned with newer commerce experiences. Any partner tooling still pointing at the legacy endpoint or relying on the old UX suddenly loses that smooth, programmatic MCA capture for new customers.
What happens if a Microsoft partner is not ready
The most immediate and painful effect is on net-new customer onboarding. If a partner has not integrated the enhanced MCA attestation API into their systems, new customers won’t be able to glide through the usual, partner-hosted sign-up and purchasing flow.
Instead, this is what will happen:
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When a partner tries to place orders for a net-new customer without a valid MCA acceptance record under the new model, the flow will require that customer to accept the MCA directly.
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Rather than staying inside the partner’s own portal UX, the customer will be redirected to the Microsoft 365 admin center (or equivalent Microsoft-owned experience) to review and accept the MCA.
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No new orders can be completed for that customer until the MCA acceptance is recorded through the Microsoft channel, which introduces friction, extra steps, and possible delays.
For partners whose value proposition includes a “single pane of glass” and a seamless ecommerce experience, this shift is a problem. It breaks the illusion of fully integrated onboarding and pushes customers into a Microsoft-branded interface right at the moment of purchase.
How this can disrupt sales motion
For established CSPs and large partners, the risk is not simply technical—it is commercial. If the switch to the enhanced API has not been completed, several things can go wrong in the sales funnel:
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Longer time-to-close for net-new customers: Sales reps may think they are about to finalize orders, only to discover that the customer must jump out to a Microsoft 365 admin center flow to accept the MCA before anything can be provisioned.
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Higher abandonment risk: Some prospects may drop off when faced with an unfamiliar Microsoft admin experience, especially in smaller organizations where the buyer and the person with admin credentials are different people.
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Support and confusion spikes: Account managers and support teams may see a spike in “why can’t I place this order?” tickets as internal teams and customers learn the new behavior the hard way.
In short, partners who missed the migration window will see their automation and UX investments diminished overnight. Instead of the partner-controlled flow quietly capturing MCA acceptance in the background via API, Microsoft’s own portal becomes the gatekeeper.
Why Microsoft is forcing the legacy API out
From Microsoft’s perspective, retiring the legacy MCA attestation API and UX is part of a broader effort to standardize and harden commerce and contract acceptance across its ecosystem. Over the past several years, Microsoft has been moving toward more consistent commercial experiences, consolidating licensing, billing, and subscription management under common platforms and APIs.
Key drivers include:
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Consistency and compliance: The enhanced MCA attestation API provides a more modern and rigorously defined contract model, which improves traceability and compliance for both Microsoft and partners.
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Security and data integrity: Phasing out older endpoints reduces the attack surface and encourages partners to align with newer, better-documented flows that handle identity and consent more securely.
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Future-proofing: New commerce features and offers typically assume the enhanced APIs exist. As long as the legacy API lingers, Microsoft must carry more technical debt and branching logic.
By setting a hard deadline, Microsoft forces the ecosystem to catch up rather than letting fragmented, partially updated flows persist indefinitely.
What prepared partners did ahead of January 5, 2026
Partners who took the transition seriously have spent the lead-up to January 5, 2026 doing several key things to avoid a crunch:
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Updating back-end integrations: They modified their commerce and provisioning platforms to call the enhanced MCA attestation API instead of the legacy one, adjusting to any schema or behavioral changes.
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Testing customer journeys: They ran end-to-end tests with test tenants and pilot customers to confirm that net-new onboarding still felt seamless and that MCA acceptance was properly recorded without unexpected redirects.
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Training sales and support: They briefed internal teams on any new behaviors, such as updated consent language or changes in the timing of MCA acceptance in the sales flow.
The result is that, for those partners, today is mostly a non-event: the legacy API can be turned off without any immediate user-visible impact, because the enhanced API has already taken over.
What unprepared partners should do now
If a partner is waking up on January 5, 2026 and discovering that their legacy MCA attestation integration is no longer working as expected, the priority is to stabilize customer-facing workflows and then catch up on the technical side.
Practical steps include:
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Acknowledge that redirects will now happen: Accept that, until the enhanced API is implemented, new customers will be forced through Microsoft’s MCA acceptance experience in the Microsoft 365 admin center. This is not ideal, but it is functional.
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Communicate clearly with sales and customers: Let internal account teams and key customers know that, for the time being, the onboarding flow includes a Microsoft-admin step to accept the MCA, and explain why it is happening so it does not look like an error.
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Prioritize integration work: Make updating to the enhanced MCA attestation API a top engineering or platform priority. The longer the old behavior persists, the more friction and possible lost deals the partner will face.
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Review automation assumptions: Some partners may have scripted or automated order placement flows that assume MCA attestation is silently handled in the background. Those scripts need to be revisited so they don’t repeatedly fail on new customers.
From a risk perspective, the situation is recoverable—partners can still transact, but their experience is degraded until the new integration is in place.
Strategic implications for the Microsoft partner ecosystem
This retirement is another signal that Microsoft expects its partners to keep pace with platform and API evolution, especially in commerce and customer identity. Relying on “it still works, so we won’t touch it” is becoming increasingly dangerous for partners whose businesses depend on tight integrations with Microsoft’s back end.
It also highlights a few trends:
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Greater Microsoft control over core contract flows: Even when partners have flexibility via APIs, Microsoft retains the right to shift where and how binding agreements like the MCA are accepted and logged.
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APIs as a moving target: Staying current with partner-center and commerce APIs is no longer optional; it is a continuous operational requirement. Roadmaps, engineering resources, and partner leadership all need to factor this in.
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Customer experience as differentiator: Partners who quickly adopt new APIs and preserve a smooth, branded UX will stand out against those who repeatedly send customers into disjointed or confusing flows.
In the end, this API retirement is a clear dividing line between partners who treat Microsoft’s commerce platform as a living, evolving dependency and those who only react when something breaks. By moving quickly to the enhanced MCA attestation API, partners can protect their sales motion, preserve a seamless onboarding experience, and stay aligned with Microsoft’s long-term direction on contracts and identity. Those who delay will still be able to transact, but increasingly on Microsoft’s terms and timelines rather than their own.
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