An Opening Journal is used to enter in the Opening and Closing Stock account values.  This can be done in the same journal used to enter in the Balance Sheet account balances or it can be done separately.

The Closing Inventory balance (P&L) should always be the same as the Inventory balance (BS).

The journal entry is against the General Ledger accounts for Purchases and the Closing Inventory.  The Purchases value will be a Debit and the Closing Inventory value with be a credit.  See example below, where the Inventory value had been entered already as  123,000.00 :

The Closing Inventory (P&L) and the Inventory (BS) should remain in tandem, as the users will either do a journal each month to adjust the balances or the user will use the Inventory Valuation Adjustment function.