In this case, simply select “I want to claim an additional refund for unused child relief” in the “Tax reliefs and deductions” section -> “Child relief or information about the relief for families 4+ and an additional refund for unused child relief”.
The additional amount to be refunded from the child relief will be filled out automatically. Once you confirm the data, the information about the additional refund for the unused child relief will be displayed and included in your tax relief.
The relief will be calculated in the eligible amount, but no more than the total of the reported social and health insurance premiums.