4. Is there a ban on corporate donations to candidates?

§ 1 Election committees shall have the right to nominate candidates for election. Electoral committees also perform other election activities, in particular, based on the principle of exclusivity, conduct campaigns for candidates
Source: Article 84 § 1, Election Code, 2011 (amended 2019)

§ 1 The financial resources of the election committee of a political party can only come from the fund the election of the party, created pursuant to the provisions of the Act of 27 June 1997 on Political Parties

§  2  The  funding  coalition  election  committee  shall  only  come  from  election  funds  of  political  parties comprising the coalition election.

§ 3 Financial resources of:
1) the election committee of an organization,
2) the voters election committee
- shall only come from the contributions of Polish citizens with their permanent domicile in the Polish Republic, and bank loans taken out solely for purposes related to elections.

§ 4 The financial resources of the election committee for the candidate for President of the Republic can only come from the contributions of Polish citizens with permanent domicile in the Polish Republic, and the election funds of political parties and bank loans taken out for purposes related to elections.
Source: Article 132 § 1-4 , Election Code, 2011 (amended 2019)

Anonymous donations, as well as contributions from foreign sources and legal entities are prohibited.
OSCE/ODIHR (2020) Republic of Poland, Parliamentary Elections, 13 October 2019. OSCE/ODIHR Limited Election Observation Mission Final Report. OSCE/ODIHR, Warsaw

According to the Electoral Code election campaigns are financed exclusively through the electoral committees, and not individual candidates. Corporate donations to electoral committees are prohibited.