Suggestions:
The system will show the different tax rate calculated for the same item is the Sales register reports. This can happen if the item is dispatched twice and the tax applied for the item is changed. Sometimes there may be a change in tax percentage after a particular period it may increase or decrease for the same item. Hence the system shows the difference in rate calculation for that particular item. Users can verify the changes in the tax chapter.
For example :
The order which is punched before 09 Sep having the tax chapter 18 % for the item OTFG0088.
And those that are punched after Sep 10 are having the tax chapter 12 % Which is right as per the master.