If a person can be claimed as a dependent on their tax return, they must answer yes to that question, even if the person who could claim them agrees not to claim them. Failing to answer yes for someone who could be claimed as a dependent by someone else, in order to get a larger stimulus payment, or avoid capital gains tax, is tax fraud.
Children over the age of 18 who are not full-time students can only be claimed as dependents if you provide more than 50% of their total financial support and they each have less than $4300 of taxable income this year. However, even if their income is more than $4300, if they do not provide more than half their own support, they will still be subject to the kiddie tax. The only way to not pay that tax is for them to say that they did provide more than half their own support. If true, no problem. If a lie, that’s fraud.
