Yes, you can club a parent or carers ad hoc bookings with their monthly contract or invoice. 

To club ad hoc bookings with a monthly invoice: 

Step 1: Set up Invoice later option for ad hoc bookings. 

To learn more about Ad hoc bookings, see the article

How to set up Ad Hoc Sessions?

Once you've set up ad hoc sessions, you can then follow the below steps. If you haven't set up your invoicing preferences for online bookings, go to your online booking dashboard > Edit Forms > Define Payment Options. Select the option to 'invoice later'. 

Step 2: Go to your online booking dashboard to view all unbilled online booking sessions.

Step 3: Run rules-based invoices to club contracts (monthly invoices) and ad-hoc sessions.