Missouri Gov. Jay Nixon has signed legislation requiring anyone younger than 17 to have written parental consent to use a booth, bed or other tanning device at a business.
The new law will require a parent or guardian to visit a tanning facility once a year and sign a consent form.
Businesses that let minors tan without parental consent could be fined $100 for a first violation, $250 for a second violation and $500 for each one after that.
Nixon said Thursday that early exposure to ultraviolet light increases the risk of skin cancer later in life.
More than 30 other states already restrict teen tanning. Missouri's law takes effect Aug. 28 but the requirements won't be enforced until the state develops a standard consent form.