Big Business 10.3 lets you change the Avg. Pay Days calculation to a specified number of days.
This Solution describes this setting (6288).
To set Avg. Pay Days Days:
1. Go to Customer Prefs
2. Click on Customer Card Prefs
3. Enter a number of days for Avg Pay Days Days, or zero for All
4. Click OK to save Customer Card Prefs
5. Click OK to save Customer Prefs