After an election has ended and the winner determined and results certified, what happens to the actual physical ballots? Are they destroyed or stored elsewhere?
For federal elections, records must be retained for twenty-two months. Otherwise, state law applies.
52 U.S. Code § 20701 - Retention and preservation of records and papers by officers of elections; deposit with custodian; penalty for violation,
Every officer of election shall retain and preserve, for a period of twenty-two months from the date of any general, special, or primary election of which candidates for the office of President, Vice President, presidential elector, Member of the Senate, Member of the House of Representatives, or Resident Commissioner from the Commonwealth of Puerto Rico are voted for, all records and papers which come into his possession relating to any application, registration, payment of poll tax, or other act requisite to voting in such election, except that, when required by law, such records and papers may be delivered to another officer of election and except that, if a State or the Commonwealth of Puerto Rico designates a custodian to retain and preserve these records and papers at a specified place, then such records and papers may be deposited with such custodian, and the duty to retain and preserve any record or paper so deposited shall devolve upon such custodian. Any officer of election or custodian who willfully fails to comply with this section shall be fined not more than $1,000 or imprisoned not more than one year, or both.
While ballots are not mentioned, specifically, the US Cybersecurity and Infrastructure Security Agency (CISA) notes:
Per federal law, all ballots, applications, and registrations related to elections for federal offices, such as those for President and Vice President, Members of the U.S. Senate or House of Representatives, must be retained and preserved for 22 months from the date of the election. In addition, many states also require specific state and local security protocols for stored ballots, such as storage in a secure vault featuring double lock systems that can only be opened when authorized representatives from both political parties are present. This requirement is intended to ensure all ballots and relevant records, such as voter registrations, cannot be discarded, but are available in case they are needed for recounts or audits to resolve any potential issues.
After expiration of the retention period, ballots are to be destroyed.