If you vote in the wrong lobby by accident you can’t undo the vote, but you can cancel its effect by crossing to the other lobby and voting on the other side, if you have time.
If your vote has been incorrectly recorded, you should inform the Clerk of Divisions in the Public Bill Office as soon as possible.
If the tellers incorrectly report the numbers, they should report the error as soon as possible and ideally before the House has proceeded to the next business. The Speaker will make a statement to the House and ask the Clerk to correct the numbers in the Journal (the record of the House’s decisions). The division will be repeated if the mistake could have reasonably made a difference to the result. If the tellers can’t agree on the numbers, the division has to be re-run.
If you have a point of order during a division, you should approach the Speaker and explain the issue.
Occasionally, the Speaker will rule that a division has been “unnecessarily claimed”. This means that the Speaker had decided that the forcing of repeated divisions by a small number of MPs is an abuse of procedure and is intended to delay the business of the House.
In these circumstances, after two minutes the Speaker will call on those who support and then on those who oppose the motion to stand up. The Speaker will then either declare the result without a division, or, if a division is needed, the Speaker will name the tellers and the division will proceed as usual.