Rushing to get your taxes done? Beware of these five mistakes tax pros say people make all the time — often without knowing it — and what you can do to avoid these expensive “learning opportunities:”

Giving the government a free loan

Sure, it might feel pretty great to get a fat refund check in April, but it actually means you made an interest-free loan to the government. Not a good idea. Try adjusting your W-4, the IRS form you give to your employer indicating how much tax to withhold from each paycheck. A federal tax calculator can help you estimate your annual tax burden more accurately.

Guessing the value of donations

Most people know to get a receipt for noncash donations, but often those receipts can become targets during an audit if you don’t have itemized lists to go with them. Figure out the thrift store value of each donated item and document it as soon as you drop it off. Many tax software programs include modules that can estimate the value of each item you donate.

Overlooking charitable donations at work

Many people give to charity via employer payroll deductions — and then overpay at tax time because they forget to deduct those donations. Keep your year-end pay stub. It should show the donations you made through your employer for the year.

Not deducting mileage

Mileage to work and the grocery store typically isn’t deductible, but mileage to and from volunteer work for IRS-recognized charities can be. Mileage for medical appointments and business activities (if you are self-employed) also may be deductible. Keep track of mileage by recording where you’re driving and why. A notebook may suffice, but there are also apps that will help you do it.

Throwing out records

People tend to keep proof of their deductions, but they often forget to keep proof of the other parts of their return. That can cause headaches, because IRS audits may involve examining bank statements. Save documents that show what went into your personal accounts. Keeping tax records for at least three years, and in some cases six years, or longer.