The party’s opening balance in the running financial year is based on the last financial closing balance. Therefore, you cannot change the opening balance of parties without entering some adjustment entries in last year.
Furthermore if you wish to change the opening balance of parties in begining financial year, you can follow these steps:
Step 1: Open BUSY and select the company you want to work with. Then, go to the Administration tab and click on Masters.
Step 2: Select Account and click on modify and choose that account which opening you want to change.
Step 3: On the account master page, you will see an option called "Op. Bal.". Here, you can edit the opening balance as per the requirements.