It really depends. If your mortgage is big enough (over 750k as of the last tax bill, which is not that uncommon in some real estate markets) or small enough (

It really depends. If your mortgage is big enough (over 750k as of the last tax bill, which is not that uncommon in some real estate markets) or small enough (so you don't itemize your tax deductions; that roughly corresponds to mortgages under $300k for married couples, I would think), then putting money into paying off the mortgage has a guaranteed 4% _after-tax_ return for some number of years that depends on where you are in your mortgage payoff cycle. Would you buy a government bond on those terms in the market? There are obviously liquidity issues with home equity that are much less of a problem with bonds, but I am also not seeing any 4.5% (generously assuming a 12.5% marginal rate on your bond interest) US treasuries bonds in the market right now, at any maturity.