Obtain Balance Sheet figures for each balance sheet account for the End of Last Financial Year. 
E.g. If going live in October 2024 and the company’s financial year runs from July-June then this would be as at 30/06/2024.

You will need to have in your file is separate columns on each line:

• the account number (this must exist in Odoo),
• the accounting date (this should be the end of the last financial year e.g. 30/06/2024),
• the journal (this should be the OPACC journal),
• the line label (e.g. "Opening Balance - Prev.Year Balances as at 30/06/2024")
• the debit amount or 
• the credit amount.
• journal number (set to OPACC01) (optional, only include if you are going to import via the opening journal items import)

The total of the debits and credits listed must balance. The file format may either be a csv or Excel file.

There are times when the Previous Year balance sheet is not ready at time of go-live because the client is waiting on their external accountant to perform some adjusting entries before the year can be closed off. It is recommended in this situation that the old system’s current Previous Year balance is imported to allow all steps to be completed. The adjustments can then be applied as an additional OPACC Journal with the same end of previous year date, so the opening balance sheet reflects these adjustments. This adjusting journal should only affect stock on hand, debtors, creditors or bank balances if there was an existing imbalance between the accounts and the sub-ledger that needed to be cleared. Otherwise, the journal should not affect these accounts to ensure the sub-ledger continues to reconcile to the corresponding balance sheet account.

Import/create an Opening Balance Journal for the last financial year. This will bring in the starting balance for balance sheet account types only.

This journal should be dated the end of last financial year. E.g. 30/06/2024 and be created against the OPACC journal.

The journal description and line labels should describe the purpose. E.g. Opening Balance June 2024.

Below: A sample opening balance journal for last financial year closing balances.

Run a balance sheet report from Odoo for the end of the previouse financial year. Compare to the balance sheet in the client’s old system for the same date. These must match. If there are any differences, then you will need to locate the issue in the imported journal, reset to draft, correct and validate.