Impeachment

Impeachment removes a sitting executive in presidential systems. Parliamentary countries use a Vote of No Confidence instead.

Live targets:

President (or equivalent national executive): two chambers. A sitting lower-chamber member files articles.
Governor: the state's legislature, as a single conviction vote. A sitting member of that state's legislature files.

President (two chambers)

House (or lower chamber). Seat-weighted simple majority of votes cast (more ayes than nays). Voting window: 6 turns. Abstentions do not count toward either side.
Senate (or upper chamber). Seat-weighted two-thirds of votes cast. Voting window: 6 turns. No votes cast fails.

If the House does not impeach, the case ends. If the Senate convicts, the executive is removed.

Governor (one chamber)

The case starts at the conviction stage. The state legislature needs two-thirds of votes cast, same Senate rule, over 6 turns.

Cooldown

After a filing, the same target cannot be impeached again for 48 turns (1 game year). That matches the VONC cooldown so repeat filings cannot grief a sitting executive.

What it is not

Impeachment is not a VONC. It is not a case. Cabinet secretaries are removed by the President, not this flow.