Tax calculations are affected by the total amount purchased. If the return contains fewer items than the original order, the tax amount may differ from the total of the tax shares of the items in the original order. For example:
The customer purchases three items at $1.09 each with a tax rate of 5%. The original tax amount will be $0.17.
If the customer exchanges each item in three separate exchanges, the tax amount will be calculated as $.06 for each exchanged item. This calculation may or may not total the original tax return credit. For example, the total of the exchanges comes to $.18, even though the refund tax credit is only $.17. This is analogous to the difference in tax calculations when, instead of buying all three items at once, the customer buys three items individually.
