If you use “consent” as your “legal basis” and you are asking for consent that is related to the offering of services over the internet (such as a web shop, a social media web site, discussion forum, ...), you need to somehow verify age (16 years normally) or be very clear that under 18 years olds (“children”) are not to access your service (and not have evidence pointing to that this is undermined)
Note that the 16 years old rule applies to “consent” only. As I stated in a separate comment “consent” is often not the way to do things. I, and many EU data protection lawyers I have met, believe consent to be a “last resort” legal basis of processing personal data. Instead, the legal basis called “legitimate interest” should normally be used where you as a company decides what is resonable, you think is needed to achieve the purposes you are processing data for, and, what the data subject would reasonable expect.
There is no under 16 age limit or age verification requirement in general for “legitimate interest”