Enable the Update Transaction Date Upon Fulfillment Status Change preference to pick items in one accounting period and ship in another accounting period.
Go to Setup -> Accounting -> Accounting Preferences -> Order Management(Subtab) -> Fulfillment Section -> Check the field “Update Transaction Date Upon Fulfillment Status Change”.
After the order status is marked Shipped, to save the order, the transaction date of the item fulfillment must be in an open accounting period and an accounting period must be selected. The period based on the shipped date shows by default in the Accounting Period field.
After this preference is enabled, NetSuite can update the transaction date based on status changes.
Note: You cannot edit, delete, or save a transaction with a Shipped status that is posting to a closed accounting period.