(1) If:
(a) a person carries on a business; and
(b) the value of all the trading stock on hand at the end of a tax year is greater than the value of all the trading stock on hand at the beginning of that tax year;
the person's ordinary income for that tax year in the form of profits from the business is to include the amount of the difference in values.
(2) If:
(a) a person carries on a business; and
(b) the value of all the trading stock on hand at the end of a tax year is less than the value of all the trading stock on hand at the beginning of that tax year;
the person's ordinary income for that tax year in the form of profits from the business is to be reduced by the amount of the difference in values.