Form 942 is the form to be filled by the employees seeking US citizenship, and Form 942 is used for fees concessions under the Application for Naturalization [N-400]. The income level of the family member(s) is seen, and if it is under the required levels of the rule, it may get the provision of a fee concession.
However, there is another form named Form i-912, which is used for applying for a fee waiver in the place of Form 942. And the requirements for Form i-912 are the income level of household member(s), the status of employment, annual income of the candidate, financial supports, total person in a household, and a signature of the application fee waiver aspirant categorically.