Carriage inwards refers to the transportation cost incurred by a business when purchasing goods from a supplier.
It is a cost that is directly related to the purchase of goods and is therefore recorded as part of the cost of goods sold.
As a result, carriage inwards is shown on the debit side of the trading account, which is used to calculate the gross profit earned by the business.
Therefore, the correct answer is "debit side of the trading account".