This error can occur in the Franking account worksheet, Opening balance Item 5 from rollover - please check & edit the item. To resolve this, follow the steps below:
Log in to HandiTax.
Select the client and the tax return.
Open the Franking Account Worksheet.
Click into the first date box under the Details of Franking Account section.
Tab through the Details of Franking Account section.
Click Save, then click Errors.