According to "Hososhiyo-sho", when the Myobo-ke (judicial officials) interpreted Yororitsuryo Sagi-ritsu (punitive clause regarding fabrication of official documents and government properties under the Yororitsuryo code) earlier, it was described that the fabrication of the Daijo Tenno Zen (a decree by the Retired Emperor) is a crime comparable to the fabrication of the Shosho (an imperial decree), which shows that the concept of inzen could have been in use early in the history. Nonetheless, the first record which mentions the term inzen is "Encho Shichi-nen Daijingu Kanchu", taken from "Dai Nihon Shiryo" (the Historical Materials of Japan) Vol.1, no.6, which was a document that, upon receipt of an imperial decree from Emperor Uda in 927, Ise-jingu Shrine issued as the Emperor Uda's instructions to Shingun (a district designated as a sanctuary which enjoyed certain privileges under an Imperial charter).
『法曹至要抄』によれば、養老律令詐偽律の解釈を巡る明法家の先例の学説として「太上天皇宣」の偽造は詔書と同一の罪に当たるとする説を挙げており早くから知られていた可能性があるが、院宣に関する記録の初見は延長(日本)7年（927年）の宇多天皇が伊勢神宮に宣旨を下されたことを受けて神宮側がその指示を神郡に向けて発した「延長七年大神宮勘注」（『大日本史料』一之六）である。