Frank, I think "deklaracja celna" might mean sth else.
What is a customs declaration?
The act whereby a person indicates the wish to place goods under a given customs procedure as provided for by the Community Customs Code (CCC) (Articles 4 (17) and 59 to 78 CC).
http://ec.europa.eu/taxation_customs/customs/procedural_aspe...Whereas this "Commerciality Statement" is read by the customs officer to the person who hasn't declared the goods as dutiable commercial goods (=hasn't made 'the customs declaration')
Perhaps "Informacja/Powiadomienie/(Oświadczenie) o wwozie towarów o charakterze handlowym" or sth similar might work better. I just don't like "deklaracja celna" or "deklaracja" as the person concerned doesn't declare anything. Besides I used to work in foreign exchange and it just rings the wrong bell in my head.