When you buy a home, covering the monthly mortgage payments may be one of your top concerns. Affording the payments—including the home’s principal, interest, homeowners insurance and property taxes—may seem easy in the beginning. But first-time homebuyers may not be planning for the reality of future property tax increases—a major oversight when considering assessed value vs market value. Your first property value assessment may be more than a surprise. The larger estimate of your home’s value, and bigger property tax bill that follows, can be downright shocking.

When we think about the cost of homeownership, a few staples immediately come to mind. Your mortgage, maintenance costs, homeowners insurance and potential HOA fees often top the list—then there are property taxes. It’s something that generated a whopping $487 billion for local governments in 2016, according to research from the Tax Policy Center.

Each year in the U.S., around 28% of Americans hire an accountant to prepare their taxes, while 34% use a tax software (like TurboTax) and 8% visit a brick-and-mortar tax preparer (like H&R Block) to get their taxes done, according to GOBankingRates. This means that over 70% of Americans don’t prepare their taxes themselves.