Expiry
The moment a fixed-payout trade closes and its result is decided by comparing the price at that moment with the entry price.
Expiry is the deadline built into every Higher/Lower trade. You don't close the trade yourself: when the expiry time arrives, the closing price is compared with the entry price, and the trade is settled as a win, a loss or a tie.
Choosing an expiry is really choosing how much noise you are willing to bet against. Very short expiries are dominated by random ticks; longer ones give a trend or a level more time to play out, but also more time for news to interfere. A useful habit is to match the expiry to the chart timeframe you analysed: an idea drawn from M5 candles rarely makes sense as a 10-second trade.
Another misunderstanding: a trade that was “winning” a minute before expiry has not won anything. Only the price at expiry counts.
On Sky Trade expiry ranges from 5 seconds to 4 hours (30 seconds minimum on market pairs), set either as a duration or as a clock time to close at. The guide choosing expiry time goes deeper.
You open Higher on EUR/USD at 1.08420 with a 5-minute expiry. Five minutes later the price is 1.08436, so the trade wins; at exactly 1.08420 it would be a tie and the stake would be refunded.