MN1 or Form T for child born in Uk

Hi everyone,
Behalf of family Member.
I need some advice please. My child was born in the UK, and now he is 10 years old. I want to register him as a British citizen. Should I fill in MN1 or T form to apply? Any help or guidance would be much appreciated. Thank you.

Is child/parents in the UK lawfully? What is the absence pattern like for the child? Can't use form T if in any of the first ten years of their life they have been absent from the UK for more than 90 days.

Form MN1 if applying on basis of a parent's ILR

Form T if applying on the basis of birth in the UK and 10 years residence in the UK. As mentioned above, absences out of the UK need to be less than 90 days in each year of the 10 years.

A Form T registration is an entitlement, not at discretion, and hence is judged more stringently to make sure that you meet the requirements of the entitlement.