We are at the process of upgrading our message to include security header messages. The current endpoint we are using to test is
For the DETERMINATION 5.7 can you please provide the updated endpoint.
Attachments: Up to 2 attachments (including images) can be used with a maximum of 512.0 KiB each and 1.0 MiB total.
This question has been answered directly to user via the DPP
OneSource Income Tax APIs