You're probably not going to have to pay them, anyway.

Concerned about estate taxes? You may not have to be. It may come as a surprise to most people, but since the end of 2012, the vast majority of people — 99.8% of all Americans — are no longer affected by the federal estate tax. Only an extremely small number of families wind up paying.

Nonetheless, some states do have their own estate taxes. So it’s still important to understand how estate taxes work, whether they will affect your family — and, if so, how much you could wind up paying. Here are a few basic concepts to understand.

Your Estate Pays the Tax — Not Your Heirs

Sometimes referred to as a “death tax,” an estate tax is essentially money that your estate — in practice, this will be your executor or anyone else who’s been charged with distributing your property to heirs — has to pay the federal and/or state government when you die and your property gets inherited.

The federal estate tax rate is a flat 40%, but as mentioned above, not every family has to pay. For one thing, as long as your spouse is a citizen, you can leave him or her any amount of property, tax free. Also, every person has a large federal estate tax “exemption” — $5.45 million in 2016 — which means you can pass along that much property to any other heirs without having to pay the federal government a cent in tax. (And you only pay the 40% on any amount that exceeds the exemption.) That exemption amount is adjusted annually for inflation, so it will continue to increase over time.

But needless to say, $5.45 million is an awfully large amount of money — which is why the federal estate tax doesn’t affect many people.

You Don’t Share Yours With Your Spouse — Until You Die

Although any individual gets a $5.45 million exemption, most couples tend to share their money — and both partners get that limit. That means a couple actually has a whopping combined exemption of $10.9 million.

This is because the federal estate tax exemption is what is known as “portable.” In simple terms, portability means that once you die, your spouse can claim your unused estate tax exemption amount, and add that to his or her own.

Your spouse would need to file an estate tax return to claim it, and it’s generally necessary to claim a deceased spouse’s exemption amount within nine months of the date of death. Wait too long and it can become expensive, or even impossible. In my work, I’ve seen numerous cases where surviving spouses believe they do not need to do anything with their deceased spouse’s estate because all assets are owned jointly. But if you’re married and own between $5.45 million and $10.9 million worth of assets, it’s extremely important to preserve the exemption amount of whichever spouse dies first. Otherwise, it may become impossible to claim it.

Your State May Take a Bite

A total of 15 states currently have an estate tax as well, and in several of those it kicks in at a lower threshold than the federal estate tax does — as low as $675,000 in New Jersey, for instance. If you live in, or own real or registered property in a state that imposes an estate tax, then your estate could be affected by that state’s estate tax.

State estate tax rates vary from state to state, but generally cap out somewhere in the low to mid teens. You can also take a deduction at the federal level for any state estate tax paid.

Your Heirs May Face a Separate Inheritance Tax

A handful of states — Iowa, Kentucky, Maryland, Nebraska, Pennsylvania, and New Jersey — have a separate inheritance tax. This is different from an estate tax: It gets paid by the heirs, not the estate; and it’s the state where you’ve been living, not where your heirs live, that determines whether they have to pay. Generally speaking, the more closely related the person who inherits the property is to the deceased individual, the lower the tax rate.

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Even though estate taxes won’t affect most Americans, it’s important to stay educated and know what they are and whether they could potentially affect your estate. In the meantime, focus on things that are most important to you — such as making sure your loved ones inherit assets in a way that makes sense, and most benefits your family.