In the middle of the 11th century Ikkoku Heikin Yaku (flat rate tax imposed from time to time) was introduced and tax system was changed so as to collect the tax just to cover the expenses required for the affairs of the Imperial court and its provincial offices; this change removed the possibility of having a tax income surplus to be stored; it is said that due to this loss of basis in the tax system, fudokoku virtually disappeared.
11世紀中期の一国平均役によって、朝廷・国衙の事業に必要な経費分だけが徴税される税制に変更されていくと、貯蔵すべき税収の余剰が出る余地も失われたために、不動穀は制度的な根拠を失って事実上消滅してしまったとされている。