The Charity Commission will run a series of adverts during the festival of Ramadan encouraging mosques and Muslim charitable organisations to register as charities.
Many Muslim groups will receive more donations than usual during the period, which runs from around 22 August to 20 September. Many do not realise registering as a charity is a legal requirement, the commission said.
A spokesman for the regulator said the adverts would be broadcast on satellite channels Islam Channel, Noor TV, Bangla TV and Iqra TV.
Ghulam Rasool, head of the Faith and Social Cohesion Unit at the commission, said: "This Ramadan we are encouraging organisations and mosques that raise funds or carry out charitable work to take a look at the Charity Commission website to find out about registering as a charity.
"Registration, which is a legal requirement for most mosques, brings many benefits, and will help you maximise the money you raise."
The unit, which is funded by a £1.2m grant from the Communities and Local Government department, has spent £30,000 making and running the adverts.
It admitted in May that its efforts to register more mosques had been slowed by the refusal of some trustees to allow visits by female outreach officers.