In law, commingling is a breach of trust in which a fiduciary mixes funds held in care for a client with his own funds, making it difficult to determine which funds belong to the fiduciary and which belong to the client. This raises particular concerns where the funds are invested, and gains or losses from the investments must be allocated. In such circumstances, the law usually presumes that any gains run to the client and any losses run to the fiduciary who is guilty of commingling. As one source puts it, "[i]n a pejorative sense, commingling is the special vice of fiduciaries in failing to keep a beneficiary's money separate from the fiduciary's own money".