No, they are fully funded by adverts and licencing their programmes to other channels and platforms. See the 4th question in this FAQ:

https://www.channel4.com/corporate/about-4/operating-respons...

There's been a fair bit of misunderstanding around Channel 4 since Nadine Dorris (ex Secretary of State for Digital, Culture, Media and Sport) aanounced plans to sell off Channel 4. A lot of people never reaslised it was publicly owned and then assumed it was the same model as the BBC, but with some adverts.

S4C (Sianel 4 Cymru, Channel 4 Wales) receives some licence fee funding (partially via the BBC making programmes for it), but it's a separate entity to Channel 4

Only the BBC gets money from the license fee. Part of the strong objection to the license fee is that BBC’s international arm already is a huge cash cow, so BBC UK could still remain ad-free.

They have a remit [0] for what content to create, but don't receive any licence fee

[0] https://www.channel4.com/corporate/about-4/what-we-do/channe...