Nowadays, Google Analytics (GA) is the trend of analytical tools. Magento default provides connection function between magento and GA. Besides, we can install other module which supports GA in order to use more functions. However, it is not sure that GA will be exactly 100%. There are some major reasons why GA tracking lacks of order from a magento Website.
2. Users turn off browse when loading order success page has not completed
3. The order is too big
The limitation of “http request” sent to GA is 8192 bytes. It means that if the order is too big( such as too many items) GA will not track this order.
4. Users prevent GA Users
Users prevent GA Users who can use add-on “Google Analytics Opt-out Browser” from collecting information.
Now, “ Google Analytics Opt- out Browser Add-on” supports Microsoft Internet Explorer 11, Google Chrome, Mozilla Firefox, Apple Safari and Opera.
Normally, with a magento website using GA, GA will miss around 10 % of total orders. If the mount of orders missed is higher than 10 %, there may be some problems which are bigger than 4 above things. You should check your website again.