From overdraft fees to late fees, Americans are collectively spending millions of dollars on unnecessary payments.

Avoiding these costly mistakes is possible with a solid budget. However, even people with a budget can make three major budgeting mistakes that could have a negative impact on their financial goals.

Major budgeting mistake number one is not knowing your income. You might know how much you make a year, but that doesn’t factor in taxes, which could cause problems in planning.

“Most people can actually tell you, ‘oh yes, I make let’s say 500 dollars a week’, but they don’t know the exact amount, so this starts their budget off with guessing how much income they bring, so then they guess how much goes out. It is a huge error that they are making,” says Tabatha Thurman, a financial education specialist with the Weokie Federal Credit Union.