Some destinations require there to be two blank pages in your passport before you enter the country. If you are running low on blank pages, some countries may issue a new passport "cross-linked", or even physically bound, to the old one. The old passport must have a blank page for the authority to endorse a cross-link. This is useful not only when a passport is running low on blank pages, but also in cases where the visa outlasts the passport that contains it.

Some countries used to offer the addition of extra pages to an existing passport (for free or a fee) at a passport office, embassy, or consulate. Due to ICAO's "write-once" policy on biometric passports, this option is not available for those who have biometric passports. The U.S. and UK no longer add extra pages to existing passports, but may offer the option of a 48 or 52-page booklet (instead of the standard 28 pages) when the passport is originally issued.

It can be possible for a person to hold multiple passports from a single country at the same time, although not all countries allow this. Even for those countries where this is allowed, it is something of a rarity; not even all immigration officials know that this is possible and legal. If you are off the beaten track, it is advisable to only show the passport that is needed for that particular border, as multiple forms of the same ID can look suspicious.

Instances where second (or even third) passports can be issued include:

• If there is little or no space left for new visas, but the current passport has valid visas that are still needed, both passports need to be valid simultaneously.
• If you need to submit your passport to two or more embassies at the same time for visas, then you need two or more passports.
• A representative of a national government (head of state, minister of government, ambassador or high commissioner) may be issued a special passport for journeys in that capacity. When not travelling on official government business, a separate standard passport is used.
• Some countries (such as Libya and Iran) will not allow entry to people whose passports show evidence of travel to Israel, so a new passport may be necessary for travel to those countries. See Israel#Get in and Visa trouble for more information.
• If a place is insisting that they require a passport as collateral (hotels, car rental), providing them the second passport not used for entry is the safer option. If they wrongfully withhold this passport, the damage done is reduced, as you still have the correct passport to clear immigration.

This is the most common type of passport issued to citizens for general international travel for both tourism and business.

See also: Diplomatic missions

As the name implies, this passport is typically issued to senior diplomats and their immediate family members, as well as high-level government officials. Visa requirements are often different.

This type of passport is generally issued to government employees, military personnel, and elected officials for work-related travel. These are often treated like diplomatic passports, although the covers will differ in color from standard or diplomatic passports.

In some countries, an internal passport is an identity document that often serves as a citizen's identity card. Only two countries issue internal passports: Russia and North Korea.

Citizens of Russia cannot be issued an internal passport at their local consulate or embassy; they must be physically present in the country to get it.

A Belarussian passport is unique in the sense that it serves as both an internal and external passport.

The Western Hemisphere Travel Initiative, a U.S. law which since 2009 has required a valid passport or other approved secure document for even the most trivial "international" trips overland between the U.S. and adjacent points (such as Canada, Mexico, Bermuda and the Caribbean), has been accompanied by a flood of specialized identity cards and trusted traveller programs. These cards do not comply with ICAO standards; they are intended as passport alternatives for travel to adjacent countries by land or sea. They are not usable for air travel.

If you live on CanUSA Street in tiny Beebe Plain, Vermont these cards will let you leave your driveway. (The road, Québec Route 247, is in Canada.)

Likewise, a Border Crossing Card issued by the U.S. government to a few trusted travellers in Mexico substitutes for both a passport card and a tourist (B2) visa.

Along the Canada-U.S. border, a few states (Michigan, New York, Vermont, and Washington) and provinces (British Columbia, Manitoba) issue an enhanced driver's license (EDL). U.S. authorities accept the card as functionally the same as a passport card, routinely accepted for re-entry into the U.S. by land or sea. Canadian authorities regard an EDL as proof of identity, but not proof of nationality, so they should be used along with a birth certificate or another proof of citizenship.

The U.S. passport card has identical requirements to the passport book, but is issued in card form for convenience. It is cheaper than a passport book (only $35), but otherwise no easier to obtain. It can be used as proof of citizenship, and for entry at land borders and seaports of WHTI countries. The Passport card cannot be used for international air travel.

U.S. state-issued enhanced driver's licenses often cost more than the $30 passport card for a validity period that is half or less. In addition, you might forfeit any existing time on your existing driver's license, and you're left with just one form of ID, instead of two. Even if a regular U.S. passport book has expired, you have five years to apply without extra fees for verification.

Canada does not issue a "passport card". Canadian passport renewals are possible if the passport expired less than a year ago, but incur the same onerous fees as a new passport ($190/5yrs or $260/10yrs, plus the photo).

If you lose your wallet, a couple of forms of alternate identification are often needed to get your driver's licence and other cards replaced. An ICAO-style standard passport, because it's separate from your other documents, is invaluable in this case.

Irish citizens may also avail of a Passport card in addition to a Passport booklet - unlike the US Passport card, the Irish Passport card is valid for air travel within the European Union and EEA and to Great Britain. At passport control, the Irish Passport card functions to all intents and purposes in the same way as an ID card issued by an EU member state.

Most European countries have some form of government-issued ID that is often mandatory to possess for every citizen above a certain age and is accepted in lieu of a passport when crossing some international borders. Within the Schengen area, this type of ID is all you need to legally cross borders, even though some airlines might think otherwise. Citizens of EEA countries can also use this ID card to enter countries on the Balkan Peninsula and Turkey (from the West, not from Iran, Iraq, Syria), despite the fact that they are not part of the EU.

Most countries in South America are members of the Mercosur organization. Citizens of such countries can travel to other Mercosur countries with just their national ID card.

The Central American countries of El Salvador, Honduras, Nicaragua, and Guatemala also allow their citizens to move freely between those countries with just a national government-issued ID card. The agreement establishing this zone of free movement further stipulates that citizens of third countries don't get charged or their passport stamped upon crossing a border between for example Honduras and El Salvador. However, the actual enforcement of this rule may very well depend on the mood of border officials.

Hong Kong permanent residents can use their identity card to enter Macau, and vice versa.

To enter mainland China, citizens of Hong Kong and Macau, are required to apply for a Home Return Permit (回鄉證/回乡证). The Chinese government does not allow them to enter using their passports. Likewise, a mainland Chinese passport is not accepted for entry into Hong Kong and Macau; mainland Chinese citizens need to obtain an Exit-Entry Permit for Travelling to and from Hong Kong and Macau (往来港澳通行证).

Taiwanese passports are not accepted for entry into mainland China due to the Chinese government's non-recognition of Taiwan as an independent country. Instead, Taiwanese citizens need to apply for a Taiwan Compatriot Pass (臺胞證/台胞证) from the Chinese government. Likewise, Chinese passports are not accepted for entry to Taiwan, and mainland Chinese citizens instead need to apply for a Taiwan Entry Permit (入臺證/入台证) from the Taiwanese government.

If your passport is lost or stolen, it may take considerable time to issue a replacement — for example, Canadian missions typically require at least 20 working days after you give them the application with all required documentation. This can be seriously inconvenient if you are abroad, especially if you have onward travel planned or if you also have to go to local authorities to replace the visa which was in the lost passport.

Many missions can also issue a temporary or emergency passport. For some countries, only one is available; for others, they are two different documents. This is much faster, e.g. for Canada three working days. Some restrictions apply to these passports. An emergency passport is usually good for only one journey and a temporary one only for a few months. Also, some countries may have different visa requirements for them; for example the Philippines provides a visa-on-arrival for holders of many passports, but anyone with an emergency or temporary passport from any country must obtain a visa in advance. Airlines will refuse to fly you without it.

A refugee or stateless person cannot obtain a passport. Under the 1951 Convention Relating to the Status of Refugees, these persons may obtain a passport-like booklet bearing the words "Travel Document" from the country in which they've taken refuge. Historically, the UN High Commission on Refugees issued documents which served a similar purpose to the individual-nation "re-entry permit" or "Certificate of Identity". As none of these confer citizenship, most countries will not allow visa-free or visa-on-arrival travel to people using these.

In Hong Kong, new immigrants who haven't become permanent residents can apply for the Document of Identity for Visa Purposes which works essentially the same as normal passports. However, document of identity holders enjoy much less visa-free privilege.

Meanwhile, Taiwanese travellers who wish to visit places which deny holders of Taiwanese passports, or simply inconvenient to apply for a Taiwan Compatriot Pass for a visit to China can also apply for a Travel Document (中华人民共和国旅行证) issued by Chinese (PRC) foreign embassies or consulates, which won't affect their Taiwanese citizenship. However, airlines and other businesses may not be familiar with Chinese travel documents, so you should prepare for explanation.

The United Nations and Interpol issue passport-like documents to a limited number of their own officials. The willingness of individual countries to accept these as stand-alone travel documents (instead of requiring they be used with a national passport) varies.

In many countries, foreigners who have been granted long-term stay or permanent residency may be required to apply for some sort of identity card issued by local authorities, which certifies additional privileges (such as multiple entry and exit) when used in conjunction with your passport.

Seasoned travellers often carry multiple photocopies of their passport (and other important documents, such as visas) when abroad. You should keep copies in locations separate from the originals, e.g. folded together in your wallet, in your luggage, or even scanned into a computer.

• This is especially useful when travelling in areas where risk of loss or theft is high. Lacking an original, a copy could save you from problems with local authorities by quickly showing them something that indicates you are authorized to be there — before they arrest you.
• Copies also may make a replacement passport easier to obtain through your embassy or consulate so you can return home. You should also make or get a copy of any entry visa required to enter a country.

Use original passports when demanded by authorities, such as when checking in for a flight, at immigration as you reach another country, or for cruise ship embarkation processing.

• If afoot, with your passport elsewhere (e.g. at your hotel), a copy and government-issued photo identification are decent substitutes that give authorities reason to check your hotel before official action.
• If cruising, unless the ship's staff states that passports are necessary for a port visit, leave them in your cabin's safe and take the copies and ID instead.

Copies are best done in color, and at least of the primary page(s) of each original. Two adjacent pages of two passports can often fit on a single sheet of copy paper.

In some countries, such as China, it may be necessary for your long-term residence or immigration status to be registered with the local police. It is advisable to give your passport to a trusted agent if you will not do this in person. Often the employer will have a staff member handle this.

Some countries require hotels to keep photocopies of your passport, both the photo and the visa page. It is not clear whether they are required to check the visa and call police if it is expired, but certainly some will refuse a room if your visa is not correct. If you don't trust hotel staff with your passport, for instance if staff have to leave the hotel premises to make a copy, you can provide your own photocopies.

Under international law it is quite legal for anyone you do business with to ask to see a passport as positive ID, and even to keep a photocopy for their records - how they use the data found on that passport will be subject to data privacy or data protection laws of the country they are in. However it is not legal to ask anyone to surrender a passport for any purpose except visa processing by the host government, things your consulate might do like renewing your passport or issuing one for your child, or when ordered to by a court of law (e.g. when the passport holder is subject to legal proceedings and is granted bail). Not "for safe keeping" or as any sort of "security guarantee". If your passport is taken for any such reason, contact your embassy or consulate; they can demand that the host government get it back for you and, at least in theory, that government is obligated to do so; typically they will contact local police who will in turn contact whoever has the passport. However, while international law is absolutely clear on this, it may not work in all countries.

Israeli passport holders, as well as anyone with an Israeli entry/exit stamp in their passport (or even any other proof of having been to Israel), will face restrictions and possibly be denied entry to many Arab or Muslim states. Similarly, entry into Israel with a passport from an Arab or Muslim state (or stamps from them) can cause long delays and possibly denial of entry.

See also: Americans in Cuba

U.S. citizens who do not get special permission from the U.S. State Department to visit Cuba have a similar problem: for a U.S. citizen to spend money in Cuba without permission from the Treasury Department is a punishable crime, and any visit is presumed to involve expenditures of money. Cuban authorities, too, will stamp a separate piece of paper, if so requested. However, multiple entry stamps to third countries like Mexico could be a red flag.

U.S. and South Korean citizens face restrictions by their respective governments from visiting North Korea. They may travel there only for approved reasons and must seek a special permit to do so from the relevant government agency.

Multiple citizenship can cause some trouble. On one hand you may have obligations that don't get enforced as long as you don't enter the country where they apply, on the other hand you may need to "pose" as a citizen of the right country during your travel – and which one is right varies.

Multiple citizenship may be especially problematic in countries that don't recognise it, and in cases where you got a non-renounceable citizenship "by accident", such as travelling to the United States just to be born, or (as a woman) marrying an immigrant from Iran.

• In many countries, you are legally required to use the passport you used to enter the country to exit from it. In most, it may cause practical difficulties, such as being accused of overstaying, if you don't.
• Equally challenging: when flying into a country, if possible you should use on entry the passport you used to check in for the flight.
• Once you've entered a country, you should generally keep using whatever passport you used to enter it for the whole time you're there. (The obvious exception is that you might want to use a different passport to check in for your flight out.)
• In some countries, such as Australia, Colombia, South Africa and the United States, you are legally required to use that country's passport to enter and exit the country if you are a citizen of it, even if you hold multiple citizenships.
• Some countries do not recognize multiple citizenship; therefore, being found in possession of another country's passport may cause you legal problems. Penalties could include stripping you of the citizenship of the country that you are in. You must also ensure that you enter the country with the passport of that country or risk being accused of entering illegally.
• Multiple citizenship does not exempt you from legal responsibilities such as military conscription or paying taxes in the countries of your nationalities – and serving in a foreign military is also grounds for loss of citizenship in many countries. There is often an exception for conscription, and agreements to avoid double taxation, but there is no general guarantee for such exceptions to apply.
• It is very unlikely that consular assistance is available from any of your other countries if you need help in a country where you are a citizen. Often a prisoner can ask to be transferred to their own country, but this option may not be available for you.
• If you have multiple citizenship, you may find yourself wanting to leave a country on one passport and then enter another country on a different passport, for instance to avoid visa fees. If you want to do this at a land border crossing, contact a consulate beforehand, in writing, to ask if it will be all right. Even if they say it'll be okay, the second country's border control may be confused by your lack of an exit stamp – if so, explain your situation; they may ask to see your other passport, but they have surely seen dual citizens before. In some countries, border officials may insist on you using the same passport on both sides of the border, so it really is important to ask first and get the answer in writing. When traveling by air, this is not typically a problem.

The countries of the Gulf Cooperation Council (Saudi Arabia, Bahrain, Kuwait, Oman, Qatar, and the United Arab Emirates) require foreigners on certain classes of visas to obtain exit visas in order to leave the country. The most notable example is those on work visas, who are required to obtain permission from their employer in order to leave the country.