At the end of a company's fiscal year, all temporary accounts should be closed. Temporary accounts accumulate balances for a single fiscal year and are then emptied. Conversely, permanent accounts accumulate balances on an ongoing basis through many fiscal years.
The most common types of temporary accounts are for revenue, expenses, gains, and losses - essentially any account that appears in the income statement. In addition, the income summary account, which is an account used to summarize temporary account balances before shifting the net balance elsewhere, is also a temporary account. Permanent accounts are those that appear on the balance sheet, such as asset, liability, and equity accounts.
At the end of the fiscal year, closing entries are used to shift the entire balance in every temporary account into retained earnings, which is a permanent account. The net amount of the balances shifted constitutes the gain or loss that the company earned during the period.
Once the year-end processing has been completed, all of the temporary accounts have been emptied and therefore "closed" for the current fiscal year. A flag in the accounting software is then set to close down the old fiscal year, which means that no one can enter transactions during that time period. Another flag can be set to open the next fiscal year, at which point the same temporary accounts are opened, now with zero balances, and are used to begin accumulating transactional information for the next fiscal year.
Thus, the only accounts closed at year end are temporary accounts. Permanent accounts remain open at all times.