The quotes functionality in Xero is not currently available via the API. If your application needs to send sales order information through to Xero we recommend you create a sales (ACCREC) invoice with a status of DRAFT.
We are planning on adding quotes functionality in future but it is not on our immediate roadmap. To help us prioritise and make sure your use case is catered for please leave your votes and comments on the Quotes User Voice page.
