It appears that an explanation about the receipt model is written in the file schema/2024-11-30-ga/invoice.md.

[shuta-ochiai]

Please provide us with the following information:

This issue is for a: (mark with an x)

- [ ] bug report -> please search issues before submitting
- [ ] feature request
- [x] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)