The term "at risk rules" refers generally to the rules under the Internal Revenue Code that the losses that are allowed for tax deduction purposes from a business operation are limited to the amount of money you can actually lose in the business. An example is that if an investor invests $100,000 in a limited partnership, the most he or she has at risk is $100,000, and his or her allowable claimed losses for tax purposes would be limited to $100,000 (and no more).