[LeeH]

I tend to agree with her on the withholding. Let's say she's overpaying by $500/month. If you run the numbers (12 payments of $500, 2% interest (typical bank rate) compounded monthly) you end up making less than $60 interest on the money in a year.

The simple fact is that most people will blow that money if they get it. If it shows up as a $6000 check after the taxes are filed, there's some chance that you might invest it. At the very least you have the $6000 and haven't piddled it away on small stuff.

But you are right... doctors aren't great money managers. The CPA firm where I used to work now specializes in doing work for doctors. Assuming they get professional accounting help, doctors tend to do what they're told, have enough income to pay their fees, and usually make enough money to have some left over to invest.