A pairing error: what to do if the pairings are wrong

Swiss pairing is a calculation: points, colours in previous rounds, who has played whom, starting number. If any of this data is wrong, so are the pairings. The most common errors:

How Swiss pairings are calculated - a Swiss system tournament.

The FIDE rules for Swiss tournaments (section C.04.2, edition from 1 February 2026) are clear: once published, pairings are not changed. There are five exceptions, and in each the chief arbiter decides - only if the change is in the interest of the tournament:

The most awkward case: the error was noticed after the round. Section C.04.2 has no direct rule for this, so arbiters follow general practice:

• • The played game stands. Nobody is made to replay it: the result was earned honestly at the board.
• • The error is fixed going forward.The correct data goes into the next round's pairing, and that evens out points and colours.
• • Played with the wrong colours. Point 4.3 names this case directly: the result stands, the colours are corrected in the records, and the next pairing uses the real colours.

For a wrongly recorded result point 4.3 sets a deadline: if it is reported to the chief arbiter within the set time after the results are published, the correction counts in the table and in the next round's pairing. If it is reported when the pairings are already made but the next round is still being played - in the pairing one round later. If after the end of the next round - it is corrected only after the tournament, for rating purposes. The deadline for complaints is set in advance, in the tournament schedule.

1. 1Stop publishing or starting the round. If the round has not started yet - do not start the clocks until the error is sorted out.
2. 2Find the source. It is almost always a wrong result, an unrecorded no-show or a forgotten latecomer, not the software itself.
3. 3Fix the data. Correct the result, withdraw the absent player, add the newcomer - in the software, not just on the wall.
4. 4Decide whether to change the pairings. Published pairings are changed only in the cases FIDE lists and by the chief arbiter's decision.
5. 5Announce and record it. Tell the players what has changed and why, and write the decision into the arbiter's report.

Two useful details. Withdrawn players are not paired again (point 3.2). And players who were paired but did not play - for example, because of a no-show - may meet again in one of the later rounds (point 3.5): an unplayed game does not count as a meeting.

• • before pairing, check all the round's results - ideally aloud with the tables;
• • check attendance: only those in the hall should be paired;
• • publish the results first, then the pairings: an error in a result is spotted before it goes into the pairings;
• • set a deadline for result complaints and announce it;
• • do not rearrange pairings by hand "for convenience" - it is forbidden.

In the Vibe Chess app Swiss pairings are made by the bbpPairings engine following the Dutch system. Most sources of error are closed by the way the tournament itself works:

• • Players enter the results, and the opponent confirms or disputes. A score error surfaces before the pairing, not after.
• • Attendance check-in before the round - only those present are paired.
• • No repeat pairings: the engine knows who has played whom.
• • Correcting a past round is done by the arbiter in their panel - the current round does not shift, and the correct score goes into the next pairing.
• • Everyone sees the pairings at once- on their phone and on the hall screen, so "we have already played" is heard before the round starts.

More about the engine - the bbpPairings engine, about the arbiter's work - arbiting a chess tournament.