Authorizations
Bearer authorization header: Bearer <token>, where <token> is the access token received from the authorization server at the end of the OAuth 2.0 flow.
Headers
Required only for Sandbox API requests; to get one, please sign up to the Developer Portal.
Path Parameters
UUID of the transaction to retrieve.
Example:
"7b7a5ed6-3903-4782-889d-b4f64bd7bef9"
Query Parameters
Use this parameter to embed the associated resources (labels, attachments and/or VAT details) of the transactions in the JSON response.
Available options: 
vat_details, labels, attachments Response
Returns the transaction identified by the id path parameter.