Is it permissible to deduct a sum of zakat paid for land on which zakat is not due from the zakat of the coming year?

It is permissible to deduct any amount paid in excess of the obligatory zakat in the past year from the zakat of the coming year, provided that it was disbursed with the intention of zakat. This was stated by Al-Mardawi in "Al-Insaf" on the authority of Imam Ahmad, and that what the collector took above his due or what the agent gifted is counted towards the zakat of a second year. Similarly, one who was wronged in his land tax (kharaj) may count it from the tithe ('ushr) or another land tax. Sheikh Taqi al-Din mentioned that what was taken in the name of zakat is counted, even if it exceeded the obligatory amount.