The day you turn 18 in the United States, you become a legal adult for almost every purpose that matters: you can vote, sign a binding lease, consent to your own medical care, enlist in any branch of the military, and be prosecuted as an adult if you break the law. A short list of things — alcohol, tobacco, handguns from licensed dealers, and some forms of gambling — still waits until 21. What you can legally do at 18 is broader than most new adults realize, and so is what you’re suddenly responsible for.
Vote and Serve on a Jury
The 26th Amendment guarantees that no U.S. citizen 18 or older can be denied the right to vote because of age.1U.S. Congress. Twenty-Sixth Amendment – Rights of Citizens Who Are Eighteen Years of Age or Older Every state except North Dakota requires you to register before casting a ballot. You can usually register online, by mail, or in person at a local election office, and some states allow same-day registration at the polls. Deadlines matter: many states cut off registration several weeks before Election Day.
Jury duty starts at the same age. Federal law requires jurors to be at least 18, U.S. citizens, and residents of the judicial district for at least one year.2Office of the Law Revision Counsel. 28 USC 1865 – Qualifications for Jury Service Active-duty military members, members of fire and police departments, and certain public officers performing official duties are exempt from federal service.3U.S. Government Publishing Office. 28 USC 1863 – Plan for Random Jury Selection State rules follow a similar framework. Ignoring a summons can bring fines or a contempt citation.
Register With the Selective Service
Almost all male U.S. citizens and male immigrants between 18 and 25 are required to register with the Selective Service System within 30 days of their 18th birthday.4Selective Service System. Who Needs to Register The requirement applies to people assigned male at birth, including those who have since changed their gender to female. People assigned female at birth are not required to register, even if they have transitioned to male. As of early 2026, Congress has not expanded the requirement to include women.
This is one of the easiest obligations to miss and one of the most expensive to skip. A conviction for failing to register can bring up to five years in prison and a fine of up to $250,000.5Selective Service System. Frequently Asked Questions Even without prosecution, non-registration disqualifies you from federal student financial aid, federal employment, and U.S. citizenship if you are an immigrant. Registration is free and takes a few minutes at sss.gov.
Be Treated as an Adult in Court
The age of majority is 18 in most states, 19 in Alabama and Nebraska, and 21 in Mississippi. Once you cross it, you are legally responsible for your own actions and obligations. Anyone harmed by what you do can sue you personally, and any judgment comes from your assets, not your parents’.
Criminal cases change even more sharply. Offenses committed at 18 or older are prosecuted in adult court. Penalties are harsher, mandatory minimums apply to some charges, and adult convictions are far harder to seal or expunge than juvenile records. A single conviction at 18 can surface in job applications, housing screenings, and professional licensing checks for years. The system treats you the same as any other adult defendant.
Sign Contracts and Build Credit
At the age of majority, you can sign binding contracts. Apartment leases, car loans, cell phone agreements, and employment contracts all become enforceable against you. Before 18, most contracts a minor signs are voidable; that protection ends on your birthday.
Credit cards come with a federal condition. Under the CARD Act, no credit card can be issued to anyone under 21 unless the applicant shows an independent ability to make the minimum payments or has a cosigner who is at least 21.6Office of the Law Revision Counsel. 15 USC 1637 – Open End Consumer Credit Plans In practice, that means a job, other verifiable income, or a cosigner. Nothing in the law prevents you from renting an apartment or buying property in your own name at 18, though landlords and lenders may require a cosigner or a larger deposit when your credit file is thin.
Make Your Own Medical Decisions
At 18, healthcare providers need your consent for treatment, not your parents’. Doctors, hospitals, and therapists must get permission directly from you, and they cannot share your health information with your parents unless you authorize it.7HHS.gov. Personal Representatives and Minors If you’re brought unconscious into an emergency room and your parents call to ask what happened, the staff may refuse to tell them anything without documentation that you gave permission.
Two documents fix this. A signed HIPAA authorization names the people who can access your medical records and speak with your doctors; you can grant broad access or limit it to narrow tasks like scheduling, and you can revoke it in writing at any time. A healthcare power of attorney goes further and gives someone you choose the legal authority to make medical decisions for you if you cannot speak for yourself. Without one, your family may have to petition a court for that authority, which takes time nobody has during a crisis.
Marry, Get a Tattoo, Register as an Organ Donor, Change Your Name
In most states, 18 is the age at which you can marry without parental consent or a judge’s approval. Nebraska requires 19, and Mississippi sets the threshold at 21.
No federal law regulates the age for getting a tattoo, but every state treats 18 as the minimum for getting tattooed without parental consent. A handful of states prohibit tattooing minors entirely, even with permission.
You can register as an organ donor through your state’s donor registry, often at the DMV. Once you sign up, that registration is legal consent for donation, and no one, including your family, can override it.8organdonor.gov. Organ Donation FAQ
You can also petition a court to change your legal name without a parent or guardian. The process varies by state but generally involves filing a petition, paying a fee, and in some states publishing notice in a local newspaper. Filing fees range from under $100 to several hundred dollars, with waivers available based on income. After a judge approves the change, you update your name with the Social Security Administration, the DMV, your bank, and other institutions.
Enlist and Take Jobs That Were Off-Limits as a Minor
You can enlist in any branch of the military — Army, Navy, Air Force, Marine Corps, Coast Guard, or Space Force — without parental consent at 18. Federal law allows enlistment at 17 with written parental permission; 18 removes that requirement.9U.S. Government Publishing Office. 10 USC 505 – Regular Components: Qualifications, Term, Grade Each branch sets its own upper age limit, with most capping between 28 and 42.10USAGov. Requirements to Join the U.S. Military
Civilian work opens up too. Many states allow 18-year-olds to serve beer, wine, and spirits as restaurant servers, even though bartending often requires 21.11APIS – Alcohol Policy Information System. Minimum Ages for On-Premises Servers and Bartenders Other jobs that restrict minors, including certain manufacturing roles, work involving hazardous materials, and overnight shifts, generally open at 18 as well.
What You Still Can’t Do
Turning 18 doesn’t unlock everything. Federal law sets the minimum age for all tobacco products — cigarettes, e-cigarettes, cigars, hookah tobacco, and nicotine liquids — at 21, with no exceptions.12U.S. Food and Drug Administration. Tobacco 21 The drinking age is 21 in every state.
Firearms split by type. Federal law allows 18-year-olds to buy rifles and shotguns from licensed dealers, but you must be 21 to buy a handgun from a licensed dealer.13Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts Some states have raised the minimum age for all firearm purchases to 21.
Gambling is a patchwork. Many states set the casino floor age at 21, especially where alcohol is served. State lotteries, bingo, and horse racing are often open at 18, but there is no uniform national standard, so check your state’s rules.
Paperwork Worth Signing on Your Birthday
Most 18-year-olds don’t think about legal documents, which is exactly the problem. The moment you turn 18, your parents lose the legal authority to make decisions for you. If an accident or medical emergency happens, they may be locked out of your care without a few basic documents already in place.
- A healthcare power of attorney, designating who can make medical decisions for you if you are incapacitated.
- A HIPAA authorization, naming specific people who can access your medical records and talk to your doctors about routine matters like test results and insurance.
- A basic will, which controls what happens to your bank accounts, car, digital assets, and personal belongings. Without one, state law decides who inherits.
None of these requires a lawyer, though consulting one is worthwhile if your situation is complicated. Most can be completed with standard state forms, a notary, and the witnesses your state requires.