API not accepting negitive line amounts

Hi Tom_Fitz,

Thank you so much for your post and welcome to the Community Forum! 

I'm sorry to hear that and I do apologize for the delayed response. For any API error integration related queries we recommend raising a support request via the following link: https://apisupport.myob.com/hc/en-us/requests/new.

Feel free to post again if you have further queries and one of us will be happy to assist.
Regards,
Earl