Your practitioner can add a tip when they take payment at the end of your visit. If they do not, you get one email afterwards with a link. Either way it is optional, and the whole tip goes to your practitioner.
At the end of a home visit your practitioner takes payment on their phone. If you would like to add a tip, say so then — it goes on the same card charge as the visit, so your statement shows one payment rather than two.
If no tip was added at the visit, you get an email titled "Add a tip for …" once your practitioner marks the visit finished. It arrives once, and only if nothing was tipped already. If you would rather not tip, you can simply ignore it — nothing happens either way, and nobody is told.
The link opens a page with a few suggested amounts. Each button shows the actual dollar figure, not just a percentage, so you can see exactly what you are paying before you choose. Some studios also let you type your own amount.
Choosing an amount takes you to a secure Stripe payment page. This is a separate payment from the visit itself, which has already been paid for — a tip is never taken automatically from your card.