These days, it’s common for parents to give their adult children some financial support. But it wouldn’t take a lot to be considered independent. About three-quarters, or 76%, of Americans say that coming off a parent’s cell phone plan is one of the “ultimate signs” of adulthood, according to a recent survey of over 2,000 adults by AT&T. Roughly two-thirds, or 66%, of those polled also say they believe adult children should aim to reach this financial milestone by age 21. However, of those who pay their own cell phone bill, most waited until age 27 — and 18% didn’t start paying for their plan until age 40 or later, AT&T found.

It makes sense that paying for a cell phone plan would be a telling sign of financial freedom for many young adults, according to Carolyn McClanahan, a certified financial planner and founder of Life Planning Partners in Jacksonville, Florida. “Eventually they have to get their own car insurance because they can’t stay on their parent’s plan once they are no longer living them after they’ve finished school,” said McClanahan, a member of the CNBC Financial Advisor Council. “At 26, they have to get their own health insurance. So it is not surprising that they stayed on the family phone plan as the last break for independence.”

Adulting includes ‘micro-milestones’

Many experts argue it’s harder today for young adults to make it on their own. “Separating from a parent’s cell phone plan might seem minor, but it symbolizes something much bigger: financial independence and personal responsibility,” said Douglas Boneparth, an CFP and the president of Bone Fide Wealth in New York. “In today’s world, where young adults are often burdened by high living costs, student loans and delayed milestones like homeownership, even small acts of autonomy feel like major wins,” said Boneparth, who also is a member of CNBC’s Financial Advisor Council. According to J.D. Power, the average monthly cell phone bill is $144.