Could someone point me to any information to help me persuade the wife to my way of thinking?

The others have touched on methods you can try to use to persuade your wife that getting a refund isn't the best choice.

I will say that emotions play a big role in all things financial. When I was single, I would calculate my safe harbor level and stay within that boundary and pay the tax owed on 4/15. My DH, on the other hand, always liked to get a refund. I went through all the financial calulations and showed him what the interest would be if that money was in savings, but that didn't matter to him. He doesn't want to owe Uncle Sam come tax day.

So, we came to a compromise, I make sure we don't owe and he has accepted that the refund we get will be very small. The amount of interest we lose out on is small and it keeps the peace.

Dawn