Why does an inventory error affect two periods?

Inventory error affect two periods because the closing inventory of one accounting period will serve as the opening inventory in the next accounting period hence any error in the closing inventory will surely affect the opening inventory of the next period as well as cost of sales or goods sold.

An inventory error affects two periods because1) the ending inventory of one period will become the beginning inventory for the following period, and2) the calculation of the cost of goods sold is beginning inventory + purchases – ending inventory.

Inventory error effect two accounting periods one is for closing another one is for opening.