A trust generally functions as a replacement for a Will. Most clients are drawn to a trust due to its ability to avoid probate (unlike a Will) and the opportunity to provide ongoing support or distributions to named beneficiaries. In many ways, a trust is a superior estate planning tool to a Will.
So...if you have a trust, do you also need a Will? The short answer is "Yes." The creation of a living trust should be followed by the titling of assets in the trust. In other words, the trust needs to become the owner of the client’s assets/property. The methods and particulars of this vary from asset to asset (and in some cases involves simply naming the trust as a payable on death beneficiary) but as a general concept, the trust needs to become the owner of the assets that belong to the client. When this is done effectively, a Will is no longer needed and probate is avoided. One could, in theory, simply not prepare a Will at all in this scenario.
However, there are sometimes hiccups. I have worked with clients and families that completely forgot about a certain account or investment. Or occasionally, the client made a mistake and failed to property re-title an asset. So, what happens when an asset or two fails to make it to the trust before death? The related Will transfers it there (to the trust) upon death. This would require a probate process (only for those forgotten assets) but the Will would move those assets to the trust—where they perhaps should have been from the beginning. However, it is important to note that there are some nuances to this—as some accounts name beneficiaries—in which case a Will would be unable to “fix” a missed account. Having a Will does not to replace the necessity of re-titling assets to the trust, but it often does go a long way to help when there are oversights.