Here's how some US citizens can hold multiple passports at once

• US citizens can hold multiple valid US passports at once.
• A secondary passport can be issued when passport markings could limit entry to some countries or when visa processing prevents immediate travel.
• President Donald Trump's former campaign chairman Paul Manafort was recently discovered to have held three valid US passports.

Although it isn't widely known, US citizens can hold multiple valid US passports.

According to the US State Department, citizens may seek a second passport, but that is usually limited to cases in which certain visas or stamps in a passport would prohibit entry to another country, or when a primary passport is held up by visa delays when immediate travel is required.

People who may require a secondary passport, according to the State Department, include international flight staff, international journalists and executives of multinational companies. The matter was raised after it was revealed that Paul Manafort, President Donald Trump's former campaign chairman, held three valid US passports, according to court documents released this week.

Manafort applied 10 times for different US passports in just over 10 years, according to the documents. At the time of his indictment, Manafort had three US passports, with different ID numbers.

Although the State Department doesn't widely promote secondary passports, applying for one is relatively simple. Applicants only need a passport photo, a completed passport renewal form and a letter describing the specific reason why a second passport is needed. The fee involved is less than $135.

The first "primary" passport is valid for 10 years, while a secondary passport is only valid for up to four years.

You can get a secondary passport if certain stamps in your passport would prevent you from entering another country. For example, passport stamps from Israel may prompt countries like Iran and Syria, which don't have diplomatic relations with Israel, to deny a traveler's entry.

In that case, providing proof of previous travel stamps to Israel and completing an application to the State Department may be enough to secure a second passport.

If the visa process by an embassy or consulate is held up by significant delays, the State Department can issue a second passport if citizens need to travel immediately. In this case, the immediate flight itinerary and a detailed letter describing visa delays are required along with the completed application.

Some people can "buy" their way into another country

If you don't qualify for a second passport and don't hold citizenship in another country, some countries may grant citizenship or passports to wealthy foreigners.

Countries like Antigua and Barbuda, Grenada, Malta, the Netherlands, and Spain allow citizenship through investment. The cheapest passport available is from Dominica, a small Caribbean island, where immediate citizenship is available for an investment of $100,000.

The US also has a pathway to citizenship for wealthy investors. Foreigners who invest a minimum of $500,000, and promise to create at least 10 jobs, are eligible for the EB-5 program that often leads to permanent residency and eventual citizenship.

The future of the EB-5 is uncertain though as it has only been extended until December 8, when the legal framework supporting it set to expire. A bipartisan bill has also been drafted calling for the program. The program came under scrutiny earlier this year after it was revealed that Nicole Meyer, the sister of senior White House aide Jared Kushner, who is the son-in-law of President Donald Trump, name-dropped Kushner while giving a presentation to Chinese investors.

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