Certainly. These reports were coming out very early on as ISIL advanced through Iraq and into Syria. It was a tax that would be imposed on Christians, Yazidis, and other minorities. There were basically three options for people in minority groups, for Christians, Yazidis, Mandaeans, and so forth: convert to Islam, pay a tax, or die. It was a very blunt option for these communities. As we know, many people paid with their lives through very horrific torture and horrific deaths at the hands of ISIL. Others fled. The Yazidis, as we know, fled up into the Sinjar Mountains. Christians fled up into the KRG region. They fled to join already existing diaspora communities in countries such as Syria initially, but then certainly into Lebanon and Jordan.
It comes down to this question: will I remain loyal to my faith? Certainly in the international understanding of religious freedom there's the freedom, obviously, to practise your faith and the freedom to be free from coercion to change your faith. Conversion has to be a free act of free will.
So yes, there was a tax that ISIL was imposing on those members of religious minority communities who had refused to convert, but often it was a question of dying rather than paying a tax.