Here's the law I'm referring to:
"Additional time is allowed for a penalty kick to be taken and completed at the
end of each half of the match or extra time. When additional time is allowed,
the penalty kick is completed when, after the kick has been taken, the ball
stops moving, goes out of play, is played by any player (including the kicker)
other than the defending goalkeeper"
So you've got 2 seconds to go on the clock and you give a pen, the player hits it and the keeper parries it straight back to the player for a tap-in.
Technically this means the penalty kick is completed, so you have to wait until the player has kicked it into the open goal and blow the whistle as it's on it's way in.
I wouldn't like to be the ref to give that decision.
"Additional time is allowed for a penalty kick to be taken and completed at the
end of each half of the match or extra time. When additional time is allowed,
the penalty kick is completed when, after the kick has been taken, the ball
stops moving, goes out of play, is played by any player (including the kicker)
other than the defending goalkeeper"
So you've got 2 seconds to go on the clock and you give a pen, the player hits it and the keeper parries it straight back to the player for a tap-in.
Technically this means the penalty kick is completed, so you have to wait until the player has kicked it into the open goal and blow the whistle as it's on it's way in.
I wouldn't like to be the ref to give that decision.