Pursuant to the provisions of the Act of 16 November 2006 on Stamp Duty (consolidated text: Journal of Laws of 2018, item 1044), stamp duty applies to the submission of a document confirming the granting of a power of attorney or power of attorney or a copy thereof, extract or duplicate thereof, in court proceedings. This regulation also applies to cases heard by administrative courts, including the Supreme Administrative Court.
The submission of a power of attorney or a copy thereof, extract or duplicate thereof, entails the obligation to pay a stamp duty of PLN 17.
Stamp duty payments can only be made in cash at the tax authority's cashier's office or cashless to the account of that authority. 
The authority responsible for stamp duty on power of attorney (procuration) submitted before the Regional Administrative Court in Warsaw and the Supreme Administrative Court is the President of the Capital City of Warsaw. 
Stamp duty can be paid:
Cash at the cash desk of the Warsaw City Hall, Budget and Accounting Department for the Śródmieście District (Urząd m. st. Warszawy, Wydział Budżetowo Księgowy dla Dzielnicy Śródmieście)
address: 43 Nowogrodzka St., 00-691 Warszawa

By bank transfer to the account: Warsaw City Hall, Taxpayer Service Center (Urząd Miasta Stołecznego Warszawy, Centrum Obsługi Podatnika)
account number: 21 1030 1508 0000 0005 5000 0070
with the note (stamp duty for).

Persons paying stamp duty from outside Poland should use the following form:
Name: Śródmieście District of the Capital City of Warsaw, ul. Nowogrodzka 43, 00-691 Warsaw
SWIFT CODE: CITIPLPX
IBAN: IBAN(space)PL60 1030 1508 0000 0005 5001 0038

Exemptions from the fee
budgetary units
local government units
individuals who, when submitting a document provide a certificate of receipt of social assistance benefits due to poverty
individuals who submitting a document confirming authorizing only the collection of documents
individuals who submitting a power of attorney granted to a spouse, descendant, ascendant or sibling
subject to reciprocity, foreign states, their diplomatic missions, consular offices and armed forces, international organizations and institutions, their branches and representative offices, as well as members of their staff and other persons equivalent to them, if they are not Polish citizens and do not have permanent residence in the territory of the Republic of Poland.