72 Pa. Stat. § 5511.19
In case any person who is the owner of real estate neglects or refuses to pay any tax levied against such real property, the tax collector of such taxes may any time thereafter notify in writing the tenant in possession of any such real property, that the owner thereof has failed to pay such tax, and request the payment of such tax together with any penalties and interest due thereon by such tenant out of any rent money then due and owing, or thereafter to become due and owing to such delinquent taxpayer. Upon receipt of such notice from the tax collector, the tenant in possession of any such real property shall deduct from any rent that is then, or may thereafter become due and owing to such delinquent owner, the amount of such delinquent tax and the penalties and interest due thereon, and pay the same over to the collector of such taxes. The proper receipt for such taxes and penalties and interest, if any, paid to the tax collector by any tenant shall be a good and sufficient voucher to offset any claim that such delinquent taxpayer may have against such tenant for any rent to the amount thereof.
72 P.S. § 5511.19