How old do you have to be to get a Tattoo in Wisconsin?

There is no minimum age. The code just states that if the individual is under the age of 18, the tattooing has to take place in the presence of and with the written consent of the individual's parent or legal guardian.

North Dakota Century Code 12.1-31-13. Tattooing, branding, subdermal implants, scarifying, and piercing - Minors.