This is my fourth free CMO Excel spreadsheet. This post is going to be very short. You can find a lot of information online, so I am not going to add much. After entering the information on the “Inputs” sheet (yellow cells only), go to the “IO_PO” sheet where you will find ways of analyzing POs and IOs by changing the PSA of the collateral, and the discount market rate. Don’t forget to check the dropdown cell to let the calculations know if the discount rate is annual, semiannual, or monthly compounding.