Tax-deferred retirement accounts can hold a vast array of investments, but a few are not permitted. Here are five of the more notable exclusions.As a general rule, no type of life insurance contract may be titled as an IRA or qualified plan, or be housed in either. The exception is the incidental benefit rule, which mandates qualified plans that are intended to provide retirement benefits can include a small amount of life insurance, but the amount of the death benefit must be incidental to the plan balance. Most IRA custodians prohibit the inclusion of any derivative that has unlimited or undefined risk, like a naked call, in which an investor sells a call option on a security without owning the security. IRAs are supposed to provide retirement security, so speculative instruments like derivatives are disallowed. An IRA owner who buys an antique or collectible, like jewelry or stamps, worth thousands of dollars cannot shield the tax on the gain from its sale inside an IRA or other retirement plan. An IRA can hold real estate, but an IRA owner cannot benefit directly from the property in any way, including rental income or by living in it. Most gold or precious metal coins cannot be in an IRA. There are permitted exceptions, however, including the American Eagle, the American Gold Buffalo and the Canadian Maple Leaf. Generally, coins must be very pure in their mineral content and not be seen as a collector’s coin to be held inside an IRA.