Accounting on periodical basis
Periodic inventory is a system of inventory in which updates are made on a periodic basis. This differs from perpetual inventory systems, where updates are made as seen fit. In a periodic inventory system no effort is made to keep up-to-date records of either the inventory or the cost of goods sold.
A periodic inventory system only updates the ending inventory balance in the general ledger when a physical inventory count is conducted. Since physical inventory counts are time-consuming, few companies do them more than once a quarter or year. In the meantime, the inventory account in the accounting system continues to show the cost of the inventory that was recorded as of the last physical inventory count.