By standard, changing accounts in item records impacts all historical transactions, including those in closed periods. This is why the system shows the error: ‘The GL Impact of a transaction in a closed period cannot be changed’. In NetSuite, there is an accounting preference called ‘Do Not Update COGS and Asset Accounts on Existing Transactions When Accounts Are Changed.‘ By enabling this preference, it is possible to update COGS and Asset accounts without impacting existing transactions.
However, when updating income and expense accounts, there is a limitation, which is being addressed under Enhancement #605686 to allow changes to income accounts without affecting historical transactions.