Don't openly admit you have a one way flight Chances are they won't ask but it is officially their duty to, so be prepared with proof of some sort of onward travel. Generally speaking the only thing they ask you to fill out is the date you intend on leaving on those little slips the air-hostesses give you.

Traveling on a one-way ticket is physically possible, but it comes with significant immigration risks and airline restrictions that vary by destination. Many countries require "proof of onward travel" as a condition of entry to ensure visitors do not overstay their visas; if you cannot provide evidence of a return or onward flight, immigration officers may deny you entry. Furthermore, airlines are often legally responsible for flying "inadmissible" passengers back to their origin, so check-in agents frequently refuse to board travelers on one-way international flights unless they hold a long-stay visa, residency, or a confirmed ticket out of the destination country. To bypass this while maintaining flexibility, some travelers use "onward ticket" rental services that provide a legitimate, temporary flight reservation for a small fee, or they book a fully refundable return ticket that they cancel after clearing customs. Always check the specific entry requirements for your destination on their official consulate website before attempting to travel without a return booking.