Collectibles such as works of art, carpets, antiques, metals, gems, stamps, coins and alcoholic beverages cannot be held in these accounts. The law doesn't allow IRA funds to be invested in life insurance or collectible items. For example, due to administrative burdens, many IRA trustees don't allow IRA owners to invest IRA funds in real estate. If your IRA invests in a company, such as a limited liability company (MLP) or a limited liability company (LP), that company's revenues will be taxable at corporate tax rates (21% as of December 2020), even if the partner is an IRA.
To be safe, public accountants should emphasize investment vehicles for which established markets exist, such as stocks, mutual funds, bonds, bank certificates of deposit, annuities (although they may not be the best for an IRA, since IRA funds are already protected against taxes), real estate and select currencies. An investor in an IRA can take advantage of real estate purchased in an IRA if the transaction is carefully structured. The main issue of the rules governing IRA investments is that Congress wants IRA money to be used for retirement and wisely invested so that it is there when needed. So, while leveraged mortgage stocks, small businesses, and energy MLPs aren't technically prohibited, it's not a good idea to include them in your IRA.
IRA investments in other unconventional assets, such as limited liability companies and real estate, risk disqualifying the IRA due to prohibited transaction rules that prohibit self-trading.