Tank closure

The lid has a cap-like closure body (1) screwable on a filler neck, and a retainer comprising a lip seal (10) for sealing an annular gap between the neck and the body. An insert element (4) is fixed into the body through an open lower side of the body. The insert element supports an internal thread by which the body is fixable at the neck. The retainer is formed between the insert element and the top side of the body. The body is made of plastic. An aperture (2) in the body is closed by an air-permeable liquid-impermeable membrane (3).