How does this accounting thing work? (WHY am I getting an error that the tax rate can't be used with the account code?)
It's best to become familiar with the Xero platform and basic accounting principles before designing an integration. Xero accounts are free, and each comes with a fully functional Demo Company. The Demo company is populated with sample data to give you an idea of what items should look like. We also have an extensive Help Centre with information on each feature as well as how-to guides specific to the API. You may also want to consult with a Xero Certified Adviser who can instruct you on the accounting requirements many clients may have.