If a parent is unable to arrange to receive child maintenance directly with the child’s other parent, they may be able to apply for payments through the Government’s Child Maintenance Service.
Child maintenance is not classed as a public fund for immigration purposes so a parent can apply for this regardless of their or their child’s immigration status, including when the parent is subject to the ‘no recourse to public funds’ (NRPF) condition.
However, the parent who is caring for the child, the non-resident parent and the child must all be habitually resident in the UK. A person can be habitually resident regardless of what type of immigration status they have
See the Government information about making a child maintenance arrangement.