This error message is usually caused by missing or incorrect details in Dimensions. Essentially, in order to populate a BACS export, you must provide the sort code of the account that is making the payment.
To correct the error:
On the Financials tab, click Cashbook.
Next to the Code field, click the magnifying glass icon.
Select the required nominal bank account number
Click Bank Details
On the Account Details tab, click Edit
Update the bank account details, ensuring you add a sort code
Click Save.
There could also be an issue with the Analysis code set up. If the bank account is being Debited instead of Credited or the other way around. Please follow the below steps to check this:
Navigate to the Debtors or Creditors ledger
Click Analysis.
Find and select the required analysis code.
Here you can see whether it Debits or Credits the Bank.