The tutorial shows how to build an amortization schedule in Excel to detail periodic payments on an amortizing loan or mortgage. Loan amortization schedule. 3.4, Enter values, Loan summary. Does anyone know how to calculate the principal and interest payments after a one time extra principal payment on a mortgage in excel? Fill in the column titled "Period" with your payment dates. Input the month and year for the first payment loan within cell A8. This Excel spreadsheet makes it easy to view the amortization of a home loan with optional extra monthly payments. Dear Mr. Jagodzinski: In fulfillment of our agreement as outlined in the Letter of Engagement, Realty Economic Advisors, LLC (REA). The Maricopa Authority has assets and may attain additional assets in the future. Track your portfolio in the most efficient way.