Postal voting is popular: more than 80 percent of voters now prefer to vote by mail. Depending on voter participation, Swiss Post delivers more than two million voting envelopes to the municipalities before an election weekend. Swiss Post makes every effort to deliver the voting envelopes to the municipal offices on time. To this end, it relies on the support of the voters. For the most part, voting envelopes posted too late can no longer be delivered on time and the votes are discounted.

As many municipal offices are closed on Saturdays, the voting envelopes must be delivered to the municipality no later than the Friday before the weekend of the elections. For the Swiss parliamentary elections of 18 October 2015, Swiss Post recommends that its customers observe the following posting deadlines:

Furthermore, Swiss Post recommends franking the voting envelopes correctly as the municipalities can refuse to accept insufficiently franked envelopes.