Visas can also be single-entry, which means the visa is cancelled as soon as the holder leaves the country, double-entry, or multiple-entry, permitting multiple entries into the country with the same visa. Countries may also issue re-entry permits that allow temporarily leaving the country without invalidating the visa. Even a business visa will normally not allow the holder to work in the host country without an additional work permit.

Once issued, a visa will typically have to be used within a certain period of time, and the period of validity starts only on entry into the country. A notable exception to this is India, where the visa validity period starts at the time the visa is issued.

The validity of a visa is not the same as the authorized period of stay in the issuing country. The visa validity usually indicates when the alien can apply for entry to the country. For example, if a visa has been issued January 1st and expires March 30th, and the typical authorized period of stay in a country is 90 days, then the 90-day authorized stay starts on the day the passenger reaches the country, which has to be between January 1st and March 30th. The traveller could therefore stay in the issuing country until July 1st.

Once in the country, the validity period of a visa or authorized stay can often be extended for a fee at the discretion of immigration authorities. Overstaying a period of authorized stay given by the immigration officers is considered illegal immigration even if the visa validity period isn't over (i.e. for multiple entry visas) and a form of being "out of status" and the offender may be fined, prosecuted, deported, or even blacklisted from entering the country again.

Entering a country without a valid visa or visa exemption may result in detention and removal (deportation or exclusion) from the country. Undertaking activities that are not authorized by the status of entry (for example, working while possessing a non-worker tourist status) can result in the individual being deemed removable, in common speech an illegal alien. Such violation is not a violation of a visa, however despite the common misuse of the phrase, but a violation of status hence the term "out of status."

Even having a visa does not guarantee entry to the host country. The border crossing authorities make the final determination to allow entry, and may even cancel a visa at the border if the alien cannot demonstrate to their satisfaction that they will abide by the status their visa grants them.

Visa and immigration laws may be very different among countries. As such, aliens are advised to check with immigration lawyers for visa and immigration laws governing the countries they wish to enter and eligibility to receive visas or other immigration benefits.