Is it permissible not to disclose additional income (gifts for teaching) when applying for government "Working Tax Credit" support, knowing that disclosure reduces the amount due, and despite paying high monthly taxes even though income levels are low?

A Muslim is an example in seeking what is lawful and avoiding what is unlawful. It is not permissible for him to receive financial support unless he meets the required conditions. If the additional income is regular and in exchange for work, it must be disclosed to the entity providing the support, even if that leads to a reduction in allowances. Furthermore, the beneficiary has the right to file a complaint with the competent authority if he believes that the taxes are not commensurate with his income.