If base url is that of sandbox the response has extra information returned whereas if base url is of production, response lacks information like sales_tax_rate etc. Is it desired or is something wrong at my end, may be some company setting?
I’ve had a look at the data and it seems that your production account has the bill coming from a non-UK company, and therefore the sales tax is not VAT. For this reason it is omitted from our API response. Your sandbox data has the bill coming from a UK contact so that is where your discrepancy lies.
We should probably be smarter in the desktop UI to prevent a VAT amount from even being entered against a foreign bill, but as this is the first instance of confusion I’ve heard of around this, I’ll mark it as a bug and stick it onto our backlog with a fairly low priority. Any “VAT” figure entered against bills from foreign contacts will correctly be ignored when it comes to preparing your accounts, so this is really just a display issue.