I mentally treat my small percentage he is in Prime at any given time as just part of my bond allocation (but generally it does not get up above a few percent, anyway, even if I let it go for a while).Oh, I forgot to link you to this - very handy tool for comparing different types of bond funds, taxation-wise: https://personal.vanguard.com/us/FundsTaxEquivForYield - you can run the numbers on your