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

(3) Presidential candidates can only accept donation and other free benefits for an election campaign from
a) a natural person resident in the territory of the Slovak Republic,
b) a legal entity having its registered office in the territory of the Slovak Republic,
c) political party registered in the Slovak Republic.

(4) Presidential candidates may not accept a donation or any other consideration free of charge for an election campaign
a) state, Slovak Land Fund, municipality or higher territorial unit,
b) a legal entity whose founder or founder is the state, the Slovak Land Fund, a municipality or a higher territorial unit,
c) a legal entity in which the state, the Slovak Land Fund, a municipality or a higher territorial unit has an ownership interest,
d) civic associations, foundations, non-profit organizations providing services of general interest, non-investment funds, associations of legal entities, associations of municipalities and organizations with an international element,
e) a public institution or a legal person established by law,
f) a person for whom he or she is unable to provide the donor identification data or the identification data of the counterparty who provided other consideration free of charge,
g) a European political party and a European political foundation.
Source: § 5(3-4), Law No. 181 on the election campaign and amendments to Law No. 85 on political parties and movements, 2014 (amended 2019)

(5) An independent candidate may accept a donation and other gratuitous fulfillment for an election campaign only from entities referred to in § 5 para.3.
(6) An independent candidate may not accept a donation or other free of charge performance for an election campaign from entities referred to in § 5para.4.
Source: § 6 (5-6), Law No. 181 on the election campaign and amendments to Law No. 85 on political parties and movements, 2014 (amended 2019)

There is no ban on corporate donations to political parties with some exceptions like state companies.