country of shared heritage.) They may not usually apply for employment involving national security. In Singapore, male PRs who have been granted PR before the age of 18 have to serve national service. Most first-generation males are exempted. They may not own certain types of real estate. They are not issued the passport of that country (unless otherwise stateless or unable to obtain a passport from their country of nationality, in which case they may be entitled to a certificate of identity instead). They do not have access to the country's consular protection (some countries such as Australia allow this). They may qualify to apply for citizenship after meeting a specified period of residence. Obligations of permanent residents Permanent residents may be required to fulfill specific residence obligations to maintain their status. In some cases, permanent residency may be conditional on a certain type of employment or maintenance of a business. Many countries have compulsory military service for citizens. Some countries, such as Singapore, extend this to permanent residents. However, in Singapore, most first generation permanent residents are exempted, and only their sons are held liable for national service. In a similar approach, the United States has Selective Service, a compulsory registration for military service, which is required of all male citizens and permanent residents ages 18 to 26; this requirement theoretically applies even to those residing in the country illegally. Applications for citizenship may be denied or otherwise impeded if the applicant cannot prove having complied with this requirement. Permanent residents may be required to reside in the country offering them residence for a given minimum length of time (as in Australia and Canada). Permanent residents may lose their status if they stay outside their host country for more than a specified period of time (as in the United States). Permanent residents have the same obligations as citizens regarding taxes. Loss of status Permanent residents may lose their status if they fail to comply with residency or other obligations imposed on them. For example: They leave the country beyond a maximum number of days (varies among countries but usually more than 2 years). They become a threat to national security, or they commit serious crimes and become subject to deportation or removal from the country. Access to citizenship Usually, permanent residents may apply for citizenship by naturalization after a period of permanent residency (typically five years) in the country