BAS Showing Incorrect Dates

Why is my BAS using dates from previous BAS periods?

Providing you are calculating for the correct BAS period and you haven't missed finalising the last one - you can check this through Previous Bas Returns - this is to do with the date settings of the computer. They need to be consistent with Cashbook, the correct form should be dd/mm/yyyy -  05/03/2015

Depending on the computer's operating system, this needs to be changed in the Time and Date settings, Clock Settings, or Regional Time. Ensure the correct time zone is selected as well.

See https://support.practicalsystems.com.au/Articles?id=1100 for Windows 8 and 10

From the Start menu, click on Control Panel > Region and Language > Change the Format to English (Australia) not NOT (US).
Click OK.