Dastak was the trade permit sanctioned to the east india company by the Mughal government. Under the terms and conditions of farrukh siyar’s farman of 1717 the East India Company was entitled to trade in Bengal without paying the normal customs duty. Based on the right derived from the imperial farman, the company used to issue dastaks authorising their agents to trade customs-free within the province of Bengal.
The nawab had issued parwanas to all his officials to honour the dastaks when the company traders produced it to them on demand. According to the farman of 1717, this right of free trade covered by the dastaks was restricted to the company alone. This right, according to the farman, was not to be exercised by the company's private traders. But in practice, the private traders of the company generally abused the free trade right by producing the dastak to the chowkies of the government. But the chowkidars had reasons to believe that most of the dastaks produced by company traders were produced just to cover their own private trade. The company sold dastaks at high price not only to European private traders but also to native merchants.
Consequently, the government was losing revenue on the one hand, and the native merchants were losing their business due to unequal competition with the company and private traders, on the other. The abuse of dastak was, in fact, one of the key issues of conflicts between the nawab and the company. The problem turned into a crisis during the regime of sirajuddaula. His policy against the abuse of dastak was one of the important causes of his conflict with the company. Being unable to persuade the company to behave as regards abusing dastak, Nawab mir qasim finally abolished the inland duties altogether in order to save the local merchants from ruin. It was this action of the nawab that landed him on a war with the company and his ultimate ouster. [Sirajul Islam]