How do I identify unknown Apple subscription and pending payment?

How to see what you were charged for

1. To see your purchase history, go to reportaproblem.apple.com.
2. Sign in to your Apple Account.
3. If Family Sharing is enabled, you can see your family members’ purchases. Select the Apple Account menu and choose a family member.
4. To see the full receipt, including tax, tap or click the purchase date. Multiple purchases, including subscriptions, might be grouped onto one charge.

You can also view your Purchase History on your device.

If you still can't identify the charge

If you checked reportaproblem.apple.com and you're still not sure why you were charged, contact Apple Support.

What do you see when following the steps here under "See your purchase history on your device"?

View your purchase history for the App Store and other Apple media services - Apple Support

Are you the Organizer of a Family Plan that uses Purchase Sharing? If so, that means members are allowed to make purchases to your payment method. You are still able to view those purchases, but would need to choose their name in the in the Family Plan.

Also, what is the exact description of the charge you are seeing and where are you seeing it, including the "Pending" amount.

Here are the four usual cases, and what to do about each: Billed, but you didn’t buy? - Apple Community

If you’ve checked all of your Apple Accounts and found nothing, it’s probably case 3: fraud.