Click Dashboard
Click Attendee Module
Click Settings button
Click Registration Setup in the horizontal menu
Select Registration Fields
Click the Edit button beside the Registration Category field that contains the pricing
If you have a universal cutoff date for all or your price options, edit the Late Date / Onsite Date with the new date and time by clicking the calendar icon and selecting the new date and time
Click the Update Field button
If you have different dates define on EACH option, then
Click the Edit button beside each applicable Registration Category price option
Change the Late Date field by clicking the Calendar icon and picking a new date and time
Scroll down and click the Update Option to apply the changes.
Repeat steps for each price option.