This error can be caused many different things. After you add a mortgage, the software automatically creates a mortgage investment amount that is equal to the Principal and Interest portion of the payment. The reason it does that is because when that mortgage is paid off, the client still has to pay the taxes and insurance part to the county and to the insurance company. If you have a low discretionary income amount and your taxes and insurance portion of the mortgage payment exceed the discretionary, the plan cannot be calculated because there will be a deficit when the mortgage is paid off. Make sure that taxes and insurance payments are not included in the mortgage investment section of the "Investment" part of the software.