Submitted iPhone app for review for Testflight and Apple failed it for iPad non-compatibility...?

You cannot. All "iPhone-only" apps can be installed and run on iPads. It will appear to the app as if it is running on a 3.5" iPhone sized screen. You should test your app on an iPad or the iPad simulator at least.

I did and the UI is sized ok. The problem from my perspective is that iPad requires support for the new multitasking layout so my app now needs to look good in landscape as well as portrait... I can force each UI into portrait but do you know if will Apple reject that build?

Also, my app requires SMS login... same question, is rejection likely?

Thanks!

Multitasking support requires supporting all orientations, yes. However, multitasking support is not mandatory

Can you explain more what you mean by "SMS login"?

Telephony. User enters their phone number, we text them a registration code.

I'm still finding that multitasking support is required. Can you point me to the documentation you're seeing?

Seems like two big red flags for app review there - 1) collecting personal information (phone number), and 2) unlocking features with a mechanism other than the App Store (in-app purchase).

Requiring that would also exclude iPod Touch and iPad users, FWIW. Perhaps not a huge market but why exclude some customers if you can avoid it?

Sure. How about searching Apple documentation for "opt out of iPad multitasking".

This is the first result.

https://developer.apple.com/library/prerelease/ios/documentation/WindowsViews/Conceptual/AdoptingMultitaskingOniPad/

The compiler also provides a warning and suggests a specific solution if your app does not support all orientations.

Of course the obvious answer is to select the blue project icon on the left, select the target, then General/Deployment Info/Devices pick iPhone. Then tell App Review it is for an iPhone only. (And, obviously, runs on iPads using the iPhone simulation on the iPad).

This doesn't work (at least for TestFlight review). The iPhone build setting is happily ignored by the review team. Actually, it's worse than this. If you submit an iPhone-only app, then iOS won't try to scale your views properly because it knows its iPhone only. This doens't, however, prevent someone from running the app in the iPad simulator. Which the reviewers do because section 2.10 of the Review Guidelines says they have to.

The "obvious" answer to tell the Reviewer about it being iPhone only is also happily ignored – known from experience – and also per section 2.10. So, you may need to make your app universal in Build Settings and, at minimum, have it launch in the iPad simulator with some reasonable degree of esthetic appeal. Now, this does not mean that you cannot appeal a rejection based on iPhone only app. But who's got the time to wait and see if Apple actually responds to appeals? I used to try that, but it took a month to get a response and the response was never very helpful.

The submission process to the App Store seems to be a little different since you can target devices more specifically there. I assume the review team takes that into consideration but I don't know for sure.

This is from experience, not directly provided by Apple.

My experience is different. I have submitted an iPhone-only app to TestFlight (and a few iPhone-only apps to the App Store) with no problem. They all run on the iPad and look like a regular 4s or a double sized 4s iPhone. Section 2.10 refers to running in that 'iPhone simulation' mode on an iPad. It does not require a universal app.

This reply is incorrect. You do NOT have to make your app Universal. If it's marked iPhone only, it can and will still be run on an iPad, but will appear to the user and to the app as if it were running on a 3.5" iPhone sized screen. You don't need any iPad specific layouts; you just need to make sure it lays out properly on the 3.5" screen and doesn't fall over when you run it on an iPad.

You are correct. There is no requirement that the app be universal. My experience was that the iPhone storyboard UI would not scale properly when running in iPad simulator – it left a big black bar across the top. The storyboard uses auto-layout and is pinned properly (ie. works on all iPhone screen size variations). Here's what I did and why I say that universal was needed: I duplicated the storyboard, set the view controller up for iPad sizing, and then dynimcally load the correctly storyboard depending on userIntefaceIdiom. However, userInterfaceIdiom always returns iPhone when it's an iPhone-only app so this never loaded the iPad version. The only work around for this was to make the app universal. So, no, I didn't have to build universal but it was the only way to get the storyboard to load apropriately for an iPad screen. All of which, just get an iPhone-only app approved.

So just to keep track of where you are - you marked as 'correct answer' the answer that states "So, you may need to make your app universal" and is posted by the person who then states in a second posting the opposite conclusion "There is no requirement that the app be universal." This person goes on to explain how their original answer, which made absolutely no mention of their Storyboard experience, was based on a set of experiences specific to Storyboard.

That's a bit narrow. @junkpile said it the best: "You cannot". We've all had different experiences getting apps approved. I've updated my original post to clarify that you may have to make your app universal in order to get a correct iPad layout – which is a requirement of the review process.

Narrow, perhaps. But accurate. Nothing wrong with your post except it is not correct as you, yourself, have noted and therefore cannot be the correct answer. And again, there is no need to make your app universal. See my original post above (i.e. the 'correct answer', albeit, not recognized as such). I guess you might add, correctly, - 'if you use Storyboard auto-layout a certain way then you screw up the iPhone mode on an iPad and may need to create a universal app to get around whatever is wrong with the way you used auto-layout in Storyboard'.

Check the condescension and maybe you'd recognize that your answer didn't actually aim to help the problem.