A head for a pressurised gas tank comprises a structure having an opening, a head comprising a base disposed in the opening, and a valve assembled with the base. The base comprises a boss disposed outside the tank, at least one first channel comprising an axial part along the axis which is not open connected with the inside of the tank, and at least one radial part. The at least one radial part is pierced radially in the boss until the radial part joins the axial part. The valve has a substantially annular shape comprising a first bore corresponding to the boss in order to be able to be engaged on the boss, and at least one second channel, one end of which opens into the first bore axially in line with said at least one radial part. A tank comprising such a head is also provided.