Executive Order 5647—Inspection of Income-Tax Returns
Pursuant to the provisions of section 257(a) of the Revenue Act of 1926 and section 55 of the Revenue Act of 1928, it is hereby ordered that returns may be open to inspection by State officers for State income-tax purposes and by beneficiaries under a will, in accordance and upon compliance with the amendment, bearing even date herewith, to the rules and regulations prescribed by the Secretary of the Treasury and approved by the President, bearing date of April 13, 1926, as amended.
The White House,
June 9, 1931.
Herbert Hoover, Executive Order 5647—Inspection of Income-Tax Returns Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/361242