itemID = item.get("item_id");
organizationID = organization.get("organization_id");
itemMap = Map();
item.update("tax_name","Standard Rate");
item.update("tax_percentage","20.00");
item.update("tax_type","ItemAmount");
item.update("taxable","true");
item.update("tax_name_formatted","Standard Rate [20%]");
result = zoho.books.updateRecord("items",organizationID,itemID,itemMap,"zbooks");