We are moving all of our apps to Microsoft SSO as one of our improvement targets for our ISO accreditation. It doesn't make sense to have multiple authenticators for different apps. We will then be able to monitor any unusual sign-in activity through a single security portal. Our FD has put a lot of work into migrating over to Xero, don't want to have to tell him to find something else because it doesn't meet with policy.

SSO with Azure AD is a must have, if this is not on Xeros road map for updates and new features then it will be a deal breaker and we will need to move to a more modern SaaS accounting solution offered by a company that manages its customers needs and that keeps up with industry standards like SSO with Microsoft.

This is a deal breaker. No SSO means we will need to look elsewhere.

Also Azure B2C directory should be supported. Then we could add Xero as an authentication provider to our app.

How can a tool which such sensitive information not support MS SSO?

This is a must have feature. It is unfair that there is no SSO integration for Xero as of now.