Reporting a change in housemate?

Do I need to report a change in housemate as a change of circumstances if my rent, address, landlord, etc all stay the same?
I can’t see this as an option on the ‘report a change in circumstances’ section. It only seems to have an option for if a partner, child or lodger is moving in or out. Or if rent, address, landlord change.

But if it generated a new tenancy agreement I’m guessing I’d need to send that to them?

And, is it within 30 days that we need to report changes in circumstances?

Don’t want to get something wrong and be sanctioned!

Thanks for your help,
Chloe