Can my child get Marketplace Health Insurance if it's cheaper?

I was recently asked this question . . . 

If a child under age 26 is able to get coverage under a parent’s policy, can they get a lower cost plan with Marketplace insurance based on income if they apply themselves?

Answer:  It depends on whether the child is a dependent in the parent’s tax household.

If the under-26 child is claimed as a dependent in the parent’s tax household - and if they have access to a parent’s job-based coverage – they are not eligible for lower costs on a Marketplace plan. This is because they have access to job-based coverage.

If the child files taxes themselves, they may be eligible for lower costs on a Marketplace plan based on their income. This is true even if they have access to a parent’s job-based coverage.

But if the child is enrolled in a parent’s job-based coverage, they are not eligible for lower costs on a Marketplace plan.