1. Use the Tours → Groups item from the main menu.
  2. Find the desired group.
  3. Double click the row or click the Edit icon.
  4. Find the desired subgroup.
  5. Double click the row or click the Edit icon.
  6. Go to Calculation tab.
  7. Define calculation items for Additional service component.
  8. Select Enabled by default option.

NOTE: if this option is enabled, the additional service will automatically be marked on online booking.