How do I pay for my business subscription with my personal iPhone?

Hello,
 

Allow me to assist you in using your iPhone to pay for your subscription.

Update your Apple Billing payment details.

Here's how:

On your iPhone or iPad

1. Go to Settings, select your name, then select Payment & Shipping. You might be asked to sign in with your Apple ID. 
2. Select Add Payment Information. Enter your new payment info to reflect your current financial institution.
3. Select Done.

I'll also add the reference on how you can receive and record invoice payments in QuickBooks Online. This will help you if you're recording invoice payments.

Don't hesitate to click the Reply button if you need some clarifications. I'd be happy to help you right away. Always keep healthy and safe.