square up and Zoho books

square up and Zoho books

Since we set up the app connection between square up and Zoho books we have realised that when the amounts are getting transferred Zoho is adding VAT again making the numbers 20% more than they should be. We have checked our settings and they VAT/ Tax link and all seems correct. 
We have found that you cannot manually adjust them even if you disconnect Square so the only option is to delete all the inputs on Zoho that relate to these sales. 
Please can you help.