Are estimated taxes really estimates? Or are they taxes?

Estimated taxes are neither taxes nor estimates. They are prepayments (also referred to as quarterly payments).

All taxpayers are required to prepay their federal taxes. If you have a job, your employer withholds federal income, Social Security and Medicare taxes from each paycheck. These withholdings are prepayments. And if you are an independent contractor or have investment or retirement income, you don’t have an employer to withhold taxes. So, you must make direct payments to the IRS. It's these direct payments that are known as estimated taxes.

The prepayment requirement applies to anyone who owe more than $1,000 when they file their tax returns. Here are some examples:

You have a job, but your federal taxes are under-withheld. Maybe you claimed too many withholding exemptions.
You have a job and are also self-employed and your withholdings don’t cover all of your federal income and self-employment taxes.
You have income where there are no withholdings. For example, interest, dividends, rent and capital gains.

Tip. You may be able to avoid having to estimate your taxes and make estimated tax payments by adjusting your withholdings.

Use the Form W-4 to ask your employer to withhold an additional flat-dollar amount each pay period.
If you have retirement income, you can often choose to have federal (and sometimes state) taxes withheld from pension, 401(k), IRA and Social Security payments.

What happens if you don't prepay the required amount? There can be a penalty.

Important. Many states also have estimated tax requirements.