Hi,

To upload initial customer and supplier balances into Odoo using a start date as a reference, you'll need to import data into journal entries. Start by gathering all necessary information, including customer/supplier names, invoice/bill numbers, due dates, outstanding amounts, and relevant accounts (Receivable for Customers, Payable for Suppliers). Ensure your chart of accounts is properly configured with accounts for Accounts Receivable and Payable. Create a specific journal in Accounting > Configuration > Journals for these initial balance entries, setting the type to "General" to keep them separate.

Next, prepare a CSV or Excel file with columns for Date, Journal, Account, Partner, Label, Debit, and Credit. The Date should be the start date for your initial balances. For example, a row might include the date, the name of the journal you created (e.g., "Initial Balances"), the account code (e.g., 411100 for Accounts Receivable), the customer or supplier name, a description like "Initial balance for invoice INV/0001", and the debit or credit amount.

To import the data, go to Accounting > Journal Entries and click "Import". Upload your CSV/Excel file and map the columns to the corresponding fields in Odoo. Ensure the date format is correctly recognized. Validate and import the data. After importing, reconcile the entries in your bank accounts to ensure everything is correctly balanced. This process ensures that your initial balances are accurately recorded in Odoo, providing a solid foundation for your accounting records.

Reference:-

* https://www.youtube.com/watch?v=V1FfrM9n200

* https://www.cybrosys.com/blog/how-to-add-opening-balance-in-odoo-17-accounting

Hope it helps