One may not do an act to himself.

Explanation

(English-origin maxim.) A man cannot be both grantor and grantee, obligor and obligee, in the same transaction — the law requires distinct parties for a valid legal act.

Where this applies

• A man tries to sell his house to himself to reset the property tax assessment — the law won't recognize a sale where buyer and seller are the same person.
• An executor of an estate attempts to purchase estate property from himself — the transaction is void because one person cannot be both seller and buyer.
• A trustee tries to lease trust property to himself personally — the law requires two distinct parties for a valid lease.