Offer optional paid extras — nail trim, pick-up & drop-off, extra pet — that clients can add to a booking.
Add-ons are the optional extras you tack onto a booking — a nail trim, pick-up & drop-off, an extra pet, a bath. You define each one once, choose how it's charged (a flat fee or a %, and whether it's per booking, per pet, or per night/visit), then attach it to any service. When that service is booked, the add-on shows up as a tick-box that's added to the price and the invoice.
Open Services and switch to the Add-ons tab. This lists every add-on you've built, with its price. Click + New add-on to create one.

Give it a Name (e.g. Nail Trim), an Amount, and a Type — Fixed ($) for a flat fee, or Percentage (%) of the booking. Then set Applies to: Whole booking (charged once, however many pets), Per pet, or Per day/night/visit. A line underneath spells out exactly what will be charged, with a worked example.

Click Create. The add-on appears as a card on the Add-ons tab — its price, and (unless it's whole-booking) a chip showing how it's charged. Click the card any time to edit it, or the trash icon to remove it.

Attach it to the services it applies to. On the Services tab, open a service, scroll to Add-ons, and tick the ones this service offers, then Save. (Tip: if you put a per-pet add-on on a service that already charges per pet, PetPro warns you so you don't double-charge.)

Now, whenever you book a service that has add-ons, they appear as tick-box extras on the Pet & service step — anything selected is added to the booking total and flows straight through to the invoice.
