Available in Sage 50 Premium Accounting and higher.
Changes to Time Slips
If you make a mistake on a time slip, you should open the time slip in the time slips window and make an adjustment. You can also make the changes on the Service Activities Selection window just before you add billing information to the invoice.
If you decide that you want to charge a customer extra money or offer a discount, you should make the changes on the invoice itself. These changes are then tracked on the Time and Billing report under the heading Write Up/Down Amount.