The dual government system was introduced by Robert Clive in the year 1765 and was continued till the year 1772. Under this system of governance, Bengal was divided into two parts of Diwani and Nizamat.
Dual Government By Robert Clive

Dual Government
The system of administration under the diwani system was divided into Diwani and Nizamat. Diwani refers to the right to collect revenue, which was given to the company and Nizamat refers to the administrative rights which were given to nawab. Harsh measures and increased rates of interest were some techniques used by the company to collect taxes. The welfare, as well as the needs of the people, were neglected by both Nawab and the company.
Some of the brutal methods used by the British under the system were British-appointed collectors to collect revenue, people were forced to pay high rates and those who were unable to pay left the villages or at times fled from the villages. One of the reasons for the famines in Bengal in 1770 was the dual governance. This system eventually let the Company gain more and more power to the point that the effect of the Mughal Empire eventually diminished. Over the region of India, the system lasted till 1857, after which the Britishers took overall control of India, overthrowing all other rules.
Outcomes of Dual Government
The system had its own sets of outcomes, both positive and negative. On the positive side, the system led Britisher's gain control over the region and exert their rules in whatever way they wanted. This was also very negative for the citizens of India as well as for the Mughal Rule.
Due to the dual government, the Mughal Rule diminished and eventually came to an end. And on the other side, the citizens of the country were exploited by the company in the form of labor, extremely high taxes, and more atrocities. So, to conclude, the system proved to be profitable for the British East India Company but was negative for all other parties.