Answered by Shaykh Abu Usamah
If one owes zakat on previous years (and after calculating them separately, one is going to pay them this year)…When calculating this years zakat, is the zakat owed on previous years subtracted from the net amount (and treated as a liability)?
Al-Salam alaykum
Yes , unpaid Zakah from previous years is treated as a liability. This is stated in Al-Durr al-Mukhtar and its commentary Radd al-Muhtar [2.282, Dar al-Fikr 1995]
Abu Usamah