A landlord commits an offence if he knowingly lets a property to more people than it is licensed to hold.  In the interests of good management you should be aware of who is living in your property at all times.  However, if you are genuinely not aware that there are more people living in your property than it is licensed to hold then you should have a reasonable excuse. But like much else in these provisions the practical operation could be interesting!!

However, if you are knowingly accepting rent from the additional occupants, whether or not you know they are tenants, this could be taken to mean that you know that they are living in the property. If guests come to stay with the tenant then provided that they are staying there as short-term guests and are not paying rent and using the property as their main or only residence they will not count towards the number of occupants.  But just how the local authority is going to know what is happening is unclear.