The usual method for entering accounts payable opening balance is to simply enter one transaction for each outstanding invoice.
The other way to post the opening balance is to import it as an AP transaction which in the end has the same result as entering it manually.
Decide which method to use by figuring out if creating a spreadsheet with the correct layout will be less work than manually entering them. The spreadsheet layout is critical and the import will fail if it is not correct.
This should include at least the following:
- Invoice Number
- Date
- Amount
This is the minimum required to make sure that the data is aged properly. The date cannot be before that first fiscal period available for posting. Usually when starting that date is at least one year prior. If the date of the invoice is older than that just use the earliest date possible so that the aging will be at the maximum value set in company settings/Accounts payable/aging periods
Optionally you should also include:
- PO number
- Terms
- Due Date
- Memo