16. Is there a limit on the amount a donor can contribute to a political party during an election?

Source: Article V (14.1), Political Party Rules of the Kingdom of Bhutan, 2015 ​

A Political Party shall be entitled to accept voluntary contributions, financial or in kind, made by any of its registered members provided the total value of such contributions does not exceed Nu. 500,000/- per member per year or as may be fixed by the Commission from time to time. 

Source: Chapter 7 (65), Public Election Act of the Kingdom of Bhutan, 2008

No political party shall accept financial contributions or in kind contributions, other than those voluntarily offered to it by any of its registered members, of an amount or value exceeding Ngultrum 100,000/- per member per year or as may be fixed by the Election Commission from time to time.

Provided that no individual or organization, during an election period, shall sponsor meals, entertainment, donations or activity of any kind which may benefit or damage the electoral prospects of any party or candidate. 

Contribution limit is specified by the Election Commission of Bhutan based on an "annual" basis and not specific to an "election year".