Looks like something changed on the backend of Zoho Books' date format, had a bunch of clients that ran into this error : {"code":1038,"message":"JSON is not well formed"}.

Looking at the logs, I couldn't see any error in the JSON format, everything was there, customer_id, line_items, ... that's when my colleague told me : "Maybe you should check the date format".

So I decided to update my code from this : zoho.currentdate to zoho.currentdate.toString("yyyy-MM-dd")

And the error was gone!

Question to Zoho : is this going to be permanent, or is it just a hiccup that will soon go away? We used to be able to create transaction using zoho.currentdate as the date.