A couple days ago, the operations lead at a fundraising advisory firm ran into a wall that trips up a lot of organizations moving their Apple devices onto a proper management setup. She was creating managed Apple accounts for team members through Apple Business Manager, and when she sent the sign-in invitation, people got stuck. Their personal cell numbers, the ones they'd want to use for two-factor login, were already tied to their personal Apple IDs, and the system said the number was already in use as a trusted phone number for another account.
Why this happens
When you set up managed Apple accounts for a business, each person typically needs a trusted phone number for two-factor authentication. But most people already have a personal Apple ID on that same phone, using that same number. Apple doesn't love the same number acting as the trusted number across accounts in every scenario, so you can hit a conflict.
The instinct to just use the administrator's own cell number for everyone is understandable, but that's a dead end. You'd be receiving everyone's two-factor codes, and Apple also caps how many accounts a single number can be tied to, so it doesn't scale past a handful of people anyway.
The workaround we tested
On the call, we worked through setting the phone number directly on the user's profile inside Apple Business Manager before the person went through the sign-in flow themselves. The idea is to get ahead of the prompt so the individual isn't asked to supply a number that's already spoken for.
- In Apple Business Manager, open the user's profile.
- Edit the profile and add the person's own phone number there.
- Save it, then have that person run through the sign-in invitation and confirm they can complete two-factor setup.
Apple's behavior here can vary, and this kind of account setup sometimes needs a specific configuration or a hand from Apple's business support. It's worth opening a support ticket in parallel so you have their guidance if the workaround doesn't hold for every user.
The bigger picture: this is groundwork for real management
The reason to get through this setup, annoying as it is, is that it opens the door to managing those Apple devices properly. In this client's case, the plan is to connect Apple Business Manager to Microsoft Intune so their Macs are managed the same way as their Windows machines: consistent settings, security tools, and app deployment across the whole fleet.
That connection usually depends on a couple of DNS records being in place first (DNS, or Domain Name System, is the setting that tells the internet where your domain lives), so the sequence matters. You get the accounts sorted, put the DNS pieces in place, then link the management platform.
If you're mixing Macs and PCs
A lot of smaller organizations run a blend of Apple and Windows devices and never get them onto a single management approach, which means inconsistent security and a lot of manual work. Getting through the setup snags is the price of admission for treating the whole fleet as one managed group.
If you're trying to bring your Apple devices under real management alongside your Windows machines and keep hitting these kinds of setup snags, we're glad to compare notes and help you find a path through.