[Why] After An Lushan, imperial household registers were in disarray, the traditional equal-field system had wholly bankrupted, and the original poll-tax-based zu-yong-diao system could no longer fit reality. State finances stood on the brink of death-collapse. [What] Chancellor Yang Yan vigorously led tax reform, abolishing zu-yong-diao and implementing the twice-a-year tax. The new law abandoned the old logic of head taxation and instead taxed on assets and land holdings, collected in summer and autumn. [Who] Chancellor Yang Yan was an outstanding but firm-styled fiscal reformer whose policies restructured the fiscal pillar of the empire. The commoners and merchants long ground by tax burden gained a certain degree of relief under this system. [How] The implementation of the twice-yearly tax marked the fundamental historical turn of classical Chinese state fiscal logic, anchoring land rather than head count as core revenue source. It sustained mid-late-Tang central finance safety.
Why
The historic event of The Twice-a-Year Tax Reform represents a key developmental peak of the Huaxia dynastic system. The fundamental structural shift in Chinese state fiscal and tax protocols. By establishing this moral or administrative benchmark, it continues to shape the structural and philosophical fabric of ancient Chinese statecraft.