According to Germany's election review law, every individual eligible to vote in Germany can contest the validity of the election, as can groups of people eligible to vote. After each general election, there are hundreds of challenges to the results.

In their official capacity, state election supervisors, the federal election supervisor, and the president of the Bundestag can also contest the results.

The objections have ranged from incomplete voter rolls, incorrectly printed ballots, and incorrectly delivered or undelivered absentee ballots, to inadequate identity checks at polling stations, unsuitable writing equipment such as pencils in voting booths, and errors in counting votes or even the loss of a ballot box.

How does the procedure work?

Objections must be made in writing to the election review commission with the Bundestag in Berlin within two months of election day.

The Bundestag's website details how to do this and points out that it will only review the election if it is contested and will not act on its own accord.

The process is free of charge. Any objections must be stated and explained in as much detail as possible — though not before the election has taken place or after the deadline has passed.

The election review commission processes all submissions. A decision is made on each individual challenge, and each objector receives written feedback from the Bundestag.

To invalidate the results of a Bundestag election, an objection must meet two requirements. First, there must be an electoral error that violates the Federal Election Act, the Federal Election Code, or the Constitution. Secondly, the reported electoral error would have to have an impact on the distribution of seats in the Bundestag.

The review commission

The review commission has nine members, who are appointed by their parliamentary parties. 

The first objections are regularly received on the Monday after the election. They are registered and bundled thematically, and distributed among the commission members to deal with.

To process all appeals, the commission needs about a year. The committee first checks whether an appeal has been filed in due form and time. Some appeals can be answered very quickly, while others require more extensive research. 

To this end, the commission collects information from the election officials and may convene an oral hearing and examine witnesses and experts under oath. 

The commission meets behind closed doors; only oral hearings are held in public. Resolutions are passed by secret ballot, deciding by majority vote; abstentions are regarded as rejections. All decisions are recorded in writing.

If objections are rejected

The Bundestag's election review commission hands the results of its investigation and its recommendations, to parliament for a final decision. It would be up to a plenary session to decide whether a national election needs to be repeated.

Voters can also contest the recommendations prepared by the election review commission and go all the way to the Federal Constitutional Court.

According to the Federal Returning Officer's website, the number of objections tends to be around 200 or less after each federal election. A notable exception was in 1994 when the review commission received 1,453 objections, and in 2002 when it received 520. Less than four percent of those cases reached the Constitutional Court.

Even unsuccessful objections can be effective and prompt a closer look at possible mistakes that might help improve the election process. Complaints in 2012, for example, resulted in reforms of election legislation.

A German national vote has never been declared invalid.

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