Why doesn't he just change it? You can change it at any time. Or do you not want to give the government an interest free loan for a year?
I think ladyknight is saying that they usually owe
money at the end of the year. I try to keep things so that I come close to even--either I owe a few hundred or they owe me a couple hundred.
There are many things that can be used to either reduce your taxable income ("deductions") or reduce the amount of tax you owe "credits")
You can either use a specified flat amount for deductions ("standard deductions") or list everything you can find ("itemized deductions.") Younger people whose income is primarily a salary and who do not have children or own a house usually find that th standard deduction is better for them. People with complex finances usually itemize.
Examples of things you can deduct:
• Contributions to a legally-defined charity: money, things you donate (e.g clothing), and even your cost of transportation to be a volunteer.
• Business expenses not reimbursed by an employer. This can be travel, a home office, buying a uniform, computer equipment, your accountant's fees, paints (if you are an artist), cameras (if you are a photographer), guitar strings (if you are a musician), maintenance of your rental property, and many other things. This is very complicated and most people would need help.
• Investment or gambling losses--but only up to the amount you made on the stock market or at the casino. So if I lost $1000 on the slot machines and won $500 at poker, I can deduct $500 of losses. This is also complicated, especially for stocks and other investments.
• Medical expenses, if they total more than a certain percentage of your income. This could include remodeling your house to accommodate a new disability, or feeding your service dog, as well as doctor fees, medicine, etc.
• Contributions to certain retirement investments.
• Interest on your mortgage.
• Real estate taxes
There are many more. That's why it can get so complicatd.