What can you promise a client about iPhone support?
That most iPhones work and some need an application opened first, said before the client asks rather than after. Overclaiming here turns a small and well understood limitation into a credibility problem you spend the rest of the project repairing.
What to say
That recent iPhones read the tag without anything installed, and present a notification the person taps.
That older supported models need an application opened first, so a tap on those produces nothing.
That the deployment carries a printed fallback for everyone the tap does not reach.
Take NFC Tools. On iOS it requires an iPhone 7 or later running iOS 15.6 or later, and the app must be launched manually. Background reading is available from the iPhone XS and XR onwards.
Three sentences, said early, and the subject is closed rather than lurking.
What not to say
That it works on all iPhones, which is contradicted the first time somebody with an older model tries it in front of you.
A percentage of the audience, which depends on who they are and which will date. Any figure you give will be quoted back.
That an update will fix it, since the background reading line is a hardware generation rather than a software one.
And an explanation of the platform differences, which is interesting to you and is not what the client is deciding about.
Demonstrating honestly
Demonstrate on the client's own phone rather than yours, and hand it back rather than doing it for them.
Show the notification step explicitly, so they see it once with you rather than discovering it alone.
If you have an older iPhone, show that too and show the fallback working. A demonstrated limitation is a managed one.
And never troubleshoot a client's phone in a meeting. Move to the fallback and continue.
What to put in writing
The outcome rather than a device list: a person presenting a phone to the marked area gets the intended result, on phones supporting background reading.
The fallback, explicitly, as part of the deliverable rather than as a concession.
The devices you tested on, with their results, so the scope of the claim is visible.
And no percentage, no device compatibility list that will age, and no undertaking about future platform behaviour.
Frequently asked questions
Should I mention the limitation unprompted?
Yes, early and briefly. A limitation you raised is managed, and one they discover is a credibility problem.
Can I promise a percentage of users?
No. It depends on their audience, it will date, and it will be quoted back at you.
Will an update fix older iPhones?
No. Background reading is tied to a hardware generation, so it is not something a software update adds.
What belongs in the contract?
The outcome, the fallback, and the devices you tested. Not a compatibility list and not a percentage.