Residents at home during lockdown who may have seen families crammed into overcrowded HMOs are being asked to report the properties to the local council.
Slough council says there are some 3,000 HMOs in the borough, all of which should be licensed.
However the council says that many owners of HMOs have not applied for licences and, with lockdown being eased, its inspectors can now check in person.
A council spokesman says: “During the lockdown with people at home during the day, they may have spotted a property where several families live in poor conditions.
“These are the people we want to help by getting their landlords to obtain licences which means there have been basic checks made to assess the standard is acceptable.
“In addition, unregulated homes can be at the centre of anti-social behaviour in neighbourhoods.”
In the additional licence scheme operated by Slough each HMO property of up to six rooms attracts a £450 licence fee plus a £300 enforcement fee. There is an additional charge of £30 per extra room after the initial six.
There is also a selective licensing scheme subject to a charge £200 plus the £300 enforcement fee.
The council’s plea to residents includes the statement: “Those reporting important intelligence to the council are encouraged to leave their name and contact details, but are under no obligation to do so.”