Why is billing information required for an authenticator?

I am not sure what you mean when you say "authenticator". I have heard of "authentication" (a verb) but not "authenticator" (a noun).

If you mean authentication and it is asking for a payment method then you have no option but to enter one such as a credit or debit card. Read the support article Add a payment method to your Apple Account - Apple Support about how to do that.

Apple's official support articles present multiple statements* about situations requiring the presence of a payment method at times, even for free items. You do not always have to have one, but if you are encountering one of those situations then you have no option but to enter a valid payment method if you wish to continue your purchase. See Add a payment method to your Apple Account - Apple Support The payment method may not be charged if you also have account balance or the item is free, but the payment method has to be present. You might even be able to remove it again immediately once Apple has seen it.

This article lists valid payment methods for different countries but note that in this situation Apple Account balance alone apparently may not meet the requirement and you need to use another payment method until you find one that satisfies Apple's requirement (often a credit or debit card): Payment methods that you can use with your Apple Account - Apple Support .

If you have already entered a payment method, use the “Add a payment method” link above to check it. If a message appears in red there is a problem with it. If the information is still correct and current, contact your financial institution. Also check this resource --> If your payment method is declined in the App Store or iTunes Store - Apple Support

* Ref.:

Add a payment method to your Apple Account - Apple Support

"To make purchases from the App Store and use subscriptions like iCloud+ and Apple Music, you need at least one payment method on file." Note that there may be a differences between “purchasing” an app for money, and simply “getting” one for free. I get free ones with no payment method.

If you can’t download or update apps on your iPhone or iPad - Apple Support

- "You might need to have a payment method on file, even if the app that you want to download is free."

If you can’t download or update apps on your iPhone or iPad - Apple Support

- If you have any active subscriptions, you must have at least one payment method on file other than Apple ID credit.

- You might not be able to remove a payment method if you have a balance due.

Sign in to your Apple Account on the web or in your device settings - Apple Support

- "When you sign in to the App Store and other media services for the first time, you might need to add a credit card or other payment information."

How apps, content, and subscriptions from Apple are billed - Apple Support

- You can’t charge gifts to your Apple ID balance. If you send a gift or gift card, your primary payment method is charged.

- Some subscriptions might not be charged to your Apple ID balance.

What you can buy with your Apple Gift Card or Apple Account balance - Apple Support

"Some purchases might require that you have a credit card on file, even if you use your Apple Account balance to make the purchase."

Incidentally, it may depend upon the age of your account. I have one that is more than 20 years old and I have never been asked to show a payment method.

The App Store requires billing information. It's not specific to the Authenticator app.

If your accounts is in good standing the App Store usually does not request a payment method.

If there has been an issue such as a pending charge or subscription or the Apple Account is of recent creation it will request a payment method. This does not mean the app will charge you in any way shape or form. Just that your account requires a valid payment method now for some reason. There is no way around this requirement if you need to download apps or update existing ones.

Once the payment method has been verified, it can then be removed.

It will place an authorization hold on the payment method for around 99c or equivalent and should be reversed shortly once it's been verified.

MeLites86 wrote:

I have had apple products before, but now I need an authenticator and must enter my billing information. Why

I am unaware of any two-factor / multi-factor / second-factor / verifier / authenticator app that requires billing information, though there well may be some of these apps.

The App Store itself can require that information, even for free downloads. That is an Apple requirement for many (all?) Apple Accounts. Why? Donno. It is what it is. Various free apps can also include in-app purchases, and that definitely needs payment info.

All current Apple devices include a built-in authenticator (and have for a while), so an add-on app is entirely optional.

Links to information on two-factor / multi-factor / verifier authentication are in the section Set up automatic verification codes:

Use the Passwords app to create, manage, and share passwords and passkeys across Apple devices - Apple Support

Limnos wrote:

I am not sure what you mean when you say "authenticator". I have heard of "authentication" (a verb) but not "authenticator" (a noun).

They may be referring to apps that are used with multi-factor authentication. There are a number of them, actually named "Authenticator," including ones by Microsoft and Alphabet. I use one called Duo for logging into various federal government sites. I believe Passwords can also be used as an authenticator.

IdrisSeabright wrote:

They may be referring to apps that are used with multi-factor authentication. There are a number of them, actually named "Authenticator,"

Which is quite annoying. I have:

• Google Authenticator
• Microsoft Authenticator
• Yubico Authenticator
• ID.ME Authenticator

All with the same name: “Authenticator”, so I needed to learn to recognize the icons.

Apple Passwords also has authenticator functionality, but thankfully it isn’t called “Authenticator"

In most cases you only need one, because they implementation the same functionality, except for id.me (official US Government single sign-on app), which sends login prompts to it. But you could get rid of all of them except id.me.

They are more secure than most other 2 factor authentication methods; SMS is the worst, FIDO physical devices the best (e.g. Yubico keys), and Passkeys somewhere in the middle.

Lawrence Finch wrote:

Apple Passwords also has authenticator functionality, but thankfully it isn’t called “Authenticator"

That it isn't using that name may well contribute to the plethora of other authenticator apps that get installed, because people can't easily find the integrated support using the obvious searches.

Lawrence Finch wrote:

In most cases you only need one, because they implementation the same functionality, except for id.me (official US Government single sign-on app), which sends login prompts to it. But you could get rid of all of them except id.me.

Interestingly enough when I worked for the State Department many years ago we used the Microsoft Authenticator to get the codes for the state department email accounts . We only had to use ID.Me for the system access on site. But that used NFC cards too which was easier.

Lawrence Finch wrote:

In most cases you only need one, because they implementation the same functionality, except for id.me (official US Government single sign-on app), which sends login prompts to it. But you could get rid of all of them except id.me.

I'm not sure how I log into id.me as I don't have the app. I use Duo because I've been using it for years. When I was at UPenn, somehow, it was configured that I just needed to tap on the notification on my watch, didn't even need to enter anything.

For id.me you must scan some form of identification, provide a history of your addresses and some other identifying information. Once approved it is very easy to use to log into almost any government site. Some sites now require it or Login.gov, such as Social Security.

Lawrence Finch wrote:

For id.me you must scan some form of identification, provide a history of your addresses and some other identifying information. Once approved it is very easy to use to log into almost any government site.

Yes, I use it to access the IRS.

Some sites now require it or Login.gov, such as Social Security.

I use login.gov for NIH, NSF and other federal sites. Plus my personal one for SSA. It's no wonder people get confused.