Can ordering a personal use medical supplement (AHCC) in an online store from the USA along with delivery to Polish be subject to customs, tax or other postage or border charges?

The general rule is that any goods imported from abroad should be taxed and taxed. At the same time, there are a number of exceptions and concessions concerning, in particular, goods of negligible value and imported for personal use. Goods with a low value may be exempt from customs duty and VAT, for more expensive you will have to pay VAT, and for those with a high value it may be necessary to pay all customs duties, i.e. both customs duties and VAT. To the best of my knowledge, the thresholds are €22, €22 to €150 and above €150. For more expensive shipments, you may be charged a postage fee for making a customs declaration. Attention should be paid to goods subject to excise duty (e.g. containing alcohol), as they are generally excluded from these reliefs. On the other hand, medicines and medical products may be exempted from customs duty entirely. If you would like to obtain a competent interpretation of your case, you can get information from the Customs Office, a unit of the National Tax Administration or an operator (e.g. Poczta Polska or a courier who is to deliver the parcel).