14. Is there a limit on the amount a donor can contribute to a political party during a non-election specific period?

66. [...] Any real persons or legal entities other than those mentioned in the foregoing article shall be prohibited from making an in kind or cash donation worth more than two billion liras each to a political party in the same year (Annex phrase by Article 8 of Law 4778, dated 2 January 2003) or allowing the political party to use its broadcast media. [...]
Source: Article 66, Law on Political Parties, 1983 (amended 2018)

Every year, the monetary values listed in the Articles 66 and 70 of this Law herewith shall be increased as the beginning of every calendar year at the rate of revaluation determined and announced in line with the provisions of Tax Procedure Law numbered 213 and dated 4.1.1961.
Source: Additional Article 6, Law on Political Parties, 1983 (amended 2018)

There is annual indexation mechanism for the maximum limit amount. The amount of "two billion liras" given in the article 66 of Law on Political Parties is before denomination in 1995.