The requirement of diplomatic or consular legalisation for foreign public documents was abolished by convention concluded 5 October 1961 in Hague („Convention”), which applies to public documents which have been executed in the territory of one Contracting State and which have to be produced in the territory of another Contracting State.

Poland has been a signatory of Convention since 14 August 2005.

Current list of States that are parties to the Hague Convention is available here:
https://www.hcch.net/en/instruments/conventions/status-table/?cid=41

For the purposes of the Convention, the following are deemed to be public documents:

• documents emanating from an authority or an official connected with the courts or tribunals of the State, including those emanating from a public prosecutor, a clerk of a court or a process-server ("huissier de justice");
• administrative documents;
• notarial acts;
• official certificates which are placed on documents signed by persons in their private capacity, such as official certificates recording the registration of a document or the fact that it was in existence on a certain date and official and notarial authentications of signatures.

However, the present Convention shall not apply:

• to documents executed by diplomatic or consular agents;
• to administrative documents dealing directly with commercial or customs operations.

According to the Convention the only formality that may be required in order to certify the authenticity of the signature, the capacity in which the person signing the document has acted and, where appropriate, the identity of the seal or stamp which it bears, is the addition of apostille, issued by the competent authority of the State from which the document emanates.

The abovementioned certificate (apostille) shall be issued at the request of the person who has signed the document or of any bearer.

However, apostille cannot be required when either the laws, regulations, or practice in force in the State where the document is produced or an agreement between two or more Contracting States have abolished or simplified it, or exempt the document itself from legalization (certification of a document by operation of law).

In Poland apostille shall be issued by the Ministry of Foreign Affairs.

Detailed descripiton of a procedure of issuing apostille, including application form, is available at the Ministry of Foreign Affairs web page:
http://www.msz.gov.pl/pl/informacje_konsularne/apostille