[1][2] İspençe was a land-tax on non-Muslims in parts of the Ottoman Empire; its counterpart, for Muslim taxpayers, was the resm-i çift - which was set at slightly lower rate.
[3] The treasury was well aware of the difference in tax takes, and the incentive to convert; the legal reforms of Bayezid II halved some criminal penalties on non-Muslim taxpayers "so that the taxpayers shall not vanish";[4] this rule was reconfirmed a century later, in 1587.
In other cases, local taxes were imposed on non-Muslims specifically to encourage conversion.
[3] İspençe had existed in the Balkans before the Ottoman conquest; the Ottoman Empire typically adapted local taxes and institutions in each conquered area, leading to a patchwork of different taxes and rates.
The concept of İspençe, theoretically a payment in lieu of corvee labour, was derived from the Byzantine "zeugaratikion", a land tax based on the zeugarion - the area of farmland which could be ploughed by a pair of oxen.