Hi there shortcut1,
It's important that all your suppliers get paid the right amount for their services. QuickBooks Online is a great tool able to help you keep track of expenses and bills so you know the amount owed to them. I can provide some information about bill payments within QuickBooks Online.
Within QuickBooks Online, the only way to have it on file the method you pay the supplier would be in the notes section of their profile. You can add this by going to the Expenses tab, then Suppliers. Click on the name of the supplier in question, then Edit. Scroll down to the notes section, then you can add as much information about them as is allowed to fit in that field. You can also add a note to each bill payment itself when creating it within QuickBooks. The thing with both of these notes is that there isn't a way to search for them, so you'd need to go within each transaction or each supplier to see the individual notes.
I can see how being able to have other ways to track these payment methods, as well as being able to pay suppliers directly through QuickBooks would be some features you'd like to see. I recommend leaving feedback in the system by clicking on the Gear Icon, then Feedback. The comments made in that section are taken into consideration when designing new features for the software.
If you have any other questions, feel free to reach out here.
