Sky Q has two PINs that you can use to restrict viewing on Sky.
Sky TV PIN
This is used to set parental controls, make purchases and rentals, and view PIN-protected shows on your Sky Q box or device at home, as well as the downloading and viewing of recordings on a device. Your PIN is linked to your billing information and parental controls, so it's important to keep it confidential.
If you’re new to Sky: The PIN is the last four digits of your viewing card.
If you’re moving from Sky+ to Sky Q : Your Sky Q PIN is the same as the one you used on your Sky+ box. If you never changed it, it'll be the last four digits of your original viewing card.