[1] In modern-day Turkey the term continues to be in use: Gümrük vergi ve resimleri (Turkish for customs taxes and duties).
Customs duties were typically paid on the value of commodities; in the Ottoman empire, just as in modern commerce, this would fuel disagreements over the "value" of the goods being traded.
As with other Ottoman taxes, collection could be "farmed out" to a contractor who would agree to pay a fixed amount, or a percentage, to the government.
Sometimes the tax farmer might attempt to request customs duties on goods or traders which had previously been exempt.
[2] Some farmers in border areas might attempt to evade livestock taxes by claiming to each government that their livestock were on the "other" side of the border; sultan Selim ordered in 1571 that gümrük resmi would have to be paid, but some tax evasion appears to have continued.