Do you want your taxes withheld?

Do you want your taxes withheld?
I think we used to say the best thing was to not have anything with held and self-withold by putting money in a money market fund or something and earn interest instead of letting the government earn it. But a few years ago I think tax law began to include a provision that if your withholding (or estimated quarterly returns) didn't come close to your tax liability you had to pay a penalty. My understanding is NOW that makes the strategy of under with holding not a good idea.The essense of the above is correct, except the underpayment penalty and interest due has been law for a very, very long time. Perhaps it is the advent of the computer and use by the IRS that makes this very mechanical calculation virtually always checked and any discrepancies charged.