As a result of changes in the law, a lot of wills that were drafted even relatively recently may now result in a capital gains tax issue, and if you have such a will, you might want to consider revising it to save taxes.

Here’s the background: When a person dies, he or she can leave an unlimited amount of assets to a spouse without incurring the federal estate tax. If assets are left to anyone else, including children, then everything above the “exemption amount” is subject to a very significant tax.

In the past, the exemption amount was not very large. As recently as 2001, it was only $675,000. Back in 2008, it was $2 million.

So let’s suppose a couple is worth $4 million. If the husband died first and left everything to the wife, then the wife died and left everything to the children, the entire $4 million would be subject to the estate tax when the wife died, and anything over the exemption amount would be taxable.

To minimize this problem, a lot of older wills say that when the first spouse dies, some amount of assets (up to the exemption amount) will go into a trust, typically for the primary benefit of the surviving spouse. As a result, the assets that go into the trust aren’t taxable at either the husband’s death or the wife’s death.

That’s great … but in 2015, the exemption amount is now $5.43 million, so for the vast majority of people the federal estate tax is no longer an issue.

That means the trust arrangement in those older wills might no longer be necessary. In fact, in some cases it might be a tax problem.

The reason: When a person dies, any assets left to someone in their will get a “step-up” in their capital gains tax basis. So if you bought stock years ago for $20,000, and it’s worth $100,000 when you die, your heirs will inherit the stock with a capital gains basis of $100,000.

But if the first spouse to die put the stock into a trust when it was worth only $20,000, it won’t get a step-up in basis at the second spouse’s death. That means that if the stock is sold, there will be a capital gains tax on $80,000 in appreciation.

So if you have a will that was written some years ago and includes this kind of trust, it’s a good idea to have it reviewed now.

Caution: There might be many other reasons why a trust is still appropriate, including asset protection planning, providing for children of a previous marriage, and optimizing the generation-skipping transfer tax exemption. Still, now that the law has changed, it would be wise to reconsider whether your current plan achieves your goals in the best possible way.