noun
power of attorney
A legal document granting authority to act on another's behalf.
不動産の売却には代理委任状が必要です。
A power of attorney is required for the sale of real estate.
委任状 is a general letter of proxy or mandate, while 代理委任状 specifically refers to a power of attorney document.
Compound of 代理 (representation) + 委任 (delegation) + 状 (document).