Microsoft states that tax rates can be updated manually in Money Plus (and Sunset) by going to: Tools / Settings / Tax Settings / Set your filing status and see Tax Rates. You’ll note that the rate schedule hasn’t actually changed since 2011, even though the current table reads “2013 Tax Year in progress”.
What they fail to mention though is that the boxes are all grayed out and you are unable to edit the rates for Single, Married filing Jointly, Married filing separately and Head of Household, so what you have to do is select Custom and your data fields will open up to plug in new rates. Naturally then, when using the Tax Estimator module, you will also need to select Custom for Filing Status, rather than Single, Married, etc. in order to use the manually updated rates.
(The only method I know of to actually update the grayed out rates is with Hung Le’s Sunriise tool, but that isn’t an option for the average user.)