Idea description

Today, the Dynamics 365 Business Central mobile app does not support guest (B2B) accounts. When a guest user signs in, the app is unable to detect the Business Central environment hosted in the resource tenant - because guest identities authenticate through their own home Microsoft Entra tenant. The same user, on the same device, with the same account, can sign in successfully through the mobile browser, since browser-based access uses a different authentication flow.

We propose that the mobile app support tenant selection for guest users, in the same way the web client does, so that a guest user who has been granted a valid Business Central license and permissions in the host tenant can sign in to the mobile app and select the environment they have access to.

Why this matters

• The capability gap is authentication-only, not licensing or permissions. Guest users in this scenario already have valid access and can work in Business Central through the browser. The only blocker is the mobile app's inability to resolve the environment for a guest identity.
• Cross-company collaboration is a common working model. Organisations routinely bring in affiliates, group companies, contractors, and external accounting or consulting staff as guest users. Under the current behaviour, this entire population is excluded from mobile access.
• The browser fallback is not an equivalent experience. Customers report that the web client on a phone is not optimised for mobile use - it feels like viewing a desktop layout on a small screen. Users are also prompted to install the mobile app while browsing, which creates a confusing experience given that the app will not accept their account.
• The expectation is reasonable from a customer's point of view. Where a mobile app already exists and is actively promoted in-product, customers expect it to be usable regardless of whether their account is a member or a guest account in the tenant.

Proposed behaviour

1. Allow guest (B2B) users to authenticate in the mobile app against the resource tenant where their Business Central environment is hosted.
2. Provide a tenant or environment selection step in the app for accounts with access to more than one tenant, mirroring the web client experience.
3. Where guest access genuinely cannot be supported, return a clear and specific message in the app explaining that guest accounts are not supported and directing the user to the browser client - rather than a generic "environment not found" error, which suggests a licensing or configuration fault and drives unnecessary support cases.

Current workarounds

• Continue using the web browser client on mobile devices (functional, but not optimised for small screens).
• Re-provision the affected user as a local member account in the host tenant, which is often not acceptable for identity governance, licensing, or organisational reasons.