Hello, @jtstephenson
I completely understand how challenging it must be when custom transaction numbers keep reappearing despite your best efforts to remove them.
It's important to note that we may be anticipating changes to this product behavior soon. However, this doesn't mean that it will be available later.
While this functionality is unavailable, I recommend submitting Feedback so that our product developers will know that this is crucial for your business needs.
Here's how:
- Go to the Gear icon.
- Under the Profile column, select Feedback.
- Share your suggestion, then click Next.
With regards to API, you can visit the Intuit Developer page to get the information. This page also contains discussions related to web programming, and there are also a lot of experts in different programming fields.
See this page to get to Intuit Developer page: Intuit Developer.
For future reference, here's an article on receiving and recording invoice payments in QuickBooks Online: Record invoice payments in QuickBooks Online.
If you have further questions about API integration, you can comment below, and we'll respond to you as soon as possible.
