Inventory periods define a period of time in which you can post changes to inventory value. An inventory period is defined by the date on which it ends, or the ending date. When you close an inventory period, you cannot post any changes to inventory value, either expected or invoiced, before this ending date, and you cannot post any new values to inventory before the ending date. If you have open item entries in the closed period, meaning positive quantities that have not yet been consumed by (applied to) outbound transactions, you can still apply outbound quantities to these entries, even if the period is closed.
Inventory periods can be re-opened to allow posting within the period again.
Inventory period entries track the closings and re-openings of an inventory period. An inventory period with at least one inventory period entry cannot be deleted.