This article is primarily for buyers in the EU. Almost all countries have some form of taxes and/or duties but the EU has stricter guidelines than most when it comes to charging fees and duties.
As of this writing most EU countries will charge VAT for items greater than $20.00 USD. Most businesses that are located outside of the EU do not collect VAT tax at time of purchase because they do not have the authority to charge the buyer and pay the tax to the proper authority.
In addition to the VAT many receiving country postal services charge a handling fee for collecting the tax. Although the notice you receive may appear as if there was insufficient postage, the charges are taxes and fees assessed by the country not the originating post office.
Many countries that were not enforcing fees and taxes in past years have started checking more if not all incoming packages. So while you may not have been charged fees or taxes in the past it is better to be prepared for those fees when ordering from abroad.
As noted in the pinchthemuse.com policies all contents are declared as merchandise for the correct value. More information about the declaration of merchandise on customs forms in the article Customs and Contents Declaration