3. Is there a ban on corporate donations to political parties?

"There shall be no financing of political parties, independent MPs, members of the representative bodies of local and regional self-government units elected from a list of a group of voters, independent lists or lists of a group of voters and candidates by:
– foreign states, foreign political parties and foreign legal persons;
– government bodies, public companies, legal persons vested with public authority, companies and other legal persons in which the Republic of Croatia or any local and regional self-government unit has any interest or shares, as well as public and other institutions owned by the Republic of Croatia or any local and regional self-government unit;
– labour unions or employer associations;
– associations, trusts and foundations represented by central government officials, or local or regional officials;
– religious communities, humanitarian and other non-profit associations and organizations;
– natural and legal persons subject to any enforcement proceedings related to their outstanding debts due to the budget or their employees;
– local and regional self-government units, except in cases and in the manner provided for in this Act.
No donations shall be made by unidentified (anonymous) sources. Donations by unidentified (anonymous) sources shall be deemed to include donations made by donors whose details are unknown at the time of their payment or those made by donors who cannot be positively identified without additional action (e.g. donations via text messaging services, telephone answering machines, etc.).
No donations, either in cash or in kind, shall be made through third parties (intermediaries).
Any donation made from any of the ineligible sources referred to in paragraphs (1), (2) and (3) of this Article shall forthwith be reported to the State Audit Office or to the State Election Commission by a political party, independent MP, member of a representative body of a local and regional self-government unit elected from a list of a group of voters, the leader of an independent list or the leader of a list of a group of voters and a candidate, and such funds shall be paid into the state budget no later than 8 days from the date of receipt of that payment.
By way of derogation from paragraph (1)(i) of this Article, the prohibition of financing political parties, independent MPs, members of the representative bodies of local and regional self-government units, independent lists or lists of a group of voters and candidates (by foreign states, foreign political parties and foreign legal persons whose core activity consists of education in the development and promotion of democratic principles) shall not apply to the financing of educational programmes."

Source: Article 22, POLITICAL ACTIVITY AND ELECTION CAMPAIGN FINANCING ACT (consolidated text) 2013, (with 2016 amendment included)