(NEXSTAR) – The United States is just weeks away from a highly-anticipated presidential election, but not everyone will be able to exercise their right to vote on Nov. 5.

Being at least 18 years old and a U.S. citizen are general requirements for voting, but individual states have laws that prohibit voting for several reasons.

Convicted felons

In all jurisdictions except Maine, Vermont, and the nation’s capital, people convicted of felony crimes lose the right to vote while incarcerated.

In half the states, felony voting restrictions extend after incarceration, often including their time on probation or parole, according to the National Conference of State Legislatures (NCSL). In some states, convicted felons lose their voting rights indefinitely for certain crimes.

In recent years there has been a general trend toward reinstating the right to vote at some point.

Inmates in the following states won’t receive automatic restitution upon release, but will have to wait until completion of sentence (which may also include parole, probation, fines, fees and a post-sentencing waiting period or other required action): Alaska, Alabama, Arkansas, Arizona, Georgia, Delaware, Idaho, Florida, Kansas, Iowa, Louisiana, Kentucky, Missouri, Mississippi, Nebraska, Tennessee, North Carolina, Virginia, Oklahoma, Wyoming, South Carolina, South Dakota, Texas, West Virginia and Wisconsin.

See the NCSL website for more details.

Unregistered voters

Unless you live in North Dakota, you’ll need to be registered to vote before the election.

Anyone who has lived in North Dakota for 30 days before the election can vote, according to the secretary of state. Voters do, however, have to bring a valid form of ID to the polls.

About 20 states allow people to register on Election Day and then immediately cast a ballot.

The remaining states require some sort of advance registration, with deadlines ranging from three to 30 days before an election. Many of the states with voter registration deadlines more than two weeks ahead of the election are located in the South.

Those without identification

In roughly three-quarters of U.S. states you won’t be allowed to vote if you don’t have identification.

Twenty-one states request photo identification, such as a driver’s license or government-issued card, according to the National Conference of State Legislatures. Fifteen additional states accept non-photo identification, such as a utility bill or bank statement that lists a person’s name and address.

In some states, there are workarounds for people who forget their identification, such as signing an affidavit of identity or filling out a provisional ballot that will be counted if they come back with their ID or if election workers can verify their signature.

States that don’t require proof of identity use other means to verify voters, such as signatures or asking for home addresses.

People voting absentee or by mail could face additional requirements, such as getting a witness to sign their absentee ballot envelope.

Voters with mental disabilities

While the rights of voters with disabilities are protected by federal law, several states have laws under which a judge can bar people deemed “mentally incapacitated” from voting.

Other states have laws prohibiting people under legal guardianship from voting. While someone under guardianship may not have the decision-making capacity to take care of one or more of their daily needs, it may not mean that they are unqualified to vote.

Despite the Justice Department affirming the voting rights of people with disabilities earlier this year, it doesn’t appear that there has been much enforcement from the Biden administration.

Citizens of U.S. territories

Residents of U.S. territories are not able to vote in the general presidential election unless they have official residency in a state or the District of Columbia. To vote, they would have to either return to the U.S. or vote via absentee ballot.

The Electoral College process doesn’t allow people living in Puerto Rico, Guam, the U.S. Virgin Islands, Northern Mariana Islands, American Samoa, and the U.S. Minor Outlying Islands to vote.

The Associated Press contributed to this report.