Manjit Singh, Jillian Welch, "Retirement Compensation Arrangements and the Prohibited Investment and Advantage Rules", Taxation of Executive Compensation and Retirement, Special Pension Edition, Volume XVI, No. 4, 2012, p. 1041 at 1045.
In contrast [to RRSPs etc.], in the RCA context, the liability for the prohibited investment tax and the advantage tax is imposed on the custodian of the RCA but a specified beneficiary of an RCA may be held jointly and severally liable only to the extent that the specified beneficiary "participated in, assented to or acquiesced in the making of," the transaction, event or series of transactions or events that resulted in the liability. [fn. 19: Subsection 207.63 of the Act.] ….
It appears, based on discussions with Finance, that the extension of liability to both the custodian and a specified beneficiary was considered necessary to ensure that liability for the taxes could be satisfied by all potential parties that may have benefited from the prohibited investment or advantage.