U.S. citizens are exempt from the eTA requirement and must carry proper identification such as a valid U.S. passport. Lawful permanent residents of the United States who hold valid status in the U.S. are exempt from the eTA requirement.
If you don't have one, you won't be able to board your flight.
Travelers may wish to avoid buying plane tickets until they have obtained an ESTA (or a valid visa, in case the ESTA is not approved). ESTA applications may be submitted at any time prior to travel. The processing of an ESTA can take up to 72 hours.
The travel document usually arrives within 150 days (sometimes longer) after submitting your application. You can't leave the country until you have your approved travel document in hand, so you should expect to spend the 3–5 months after submitting your green card application in the United States.
Who already have a visa in their passport. Travelers may wish to avoid buying plane tickets until they have obtained an ESTA (or a valid visa, in case the ESTA is not approved). ESTA applications may be submitted at any time prior to travel. The processing of an ESTA can take up to 72 hours.
How long it takes to get an eTA. It's best to get an eTA before you book your flight to Canada. Most applicants get their eTA approval (via email) within minutes. However, some requests can take several days to process if you're asked to submit supporting documents.
Generally, to travel outside the United States, a TPS applicant must apply for a travel document (advance parole; Form I-131) and receive advance parole BEFORE leaving. This process usually takes several months.
Officers will assist you in making your declaration and will work out your personal exemption and any duty and taxes you owe in the way that benefits you most. If you return to Canada by commercial aircraft, you will receive a Form E311, CBSA Declaration Card to complete before you land.
If you are a US citizen, you must carry proof of citizenship such as a: passport. birth certificate. certificate of citizenship or naturalization. certificate of Indian status along with photo identification.
Before you arrive in Canada, you may be asked to complete a Customs Declaration Card. Complete this card before meeting with customs and immigration officials, even if you aren't a Canadian citizen. If you're traveling by air, it's a good idea to complete the card before you leave the airplane.