12 CFR 24.4: Investment limits.

(a) Limits on aggregate outstanding investments. A national bank's aggregate outstanding investments under this part may not exceed 5 percent of its capital and surplus, unless the bank is at least adequately capitalized and the OCC determines, by written approval of a written request by the bank to exceed the 5 percent limit, that a higher amount of investments will not pose a significant risk to the deposit insurance fund. In no case may a bank's aggregate outstanding investments under this part exceed 15 percent of its capital and surplus. When calculating the aggregate amount of its aggregate outstanding investments under this part, a national bank should follow generally accepted accounting principles, unless otherwise directed or permitted in writing by the OCC for prudential or safety and soundness reasons.

(b) Limited liability. A national bank may not make an investment under this part that would expose the bank to unlimited liability.