Choosing between a testamentary trust and an irrevocable trust comes down to when the trust takes effect and how much control you’re willing to give up. A testamentary trust is written into your will and only springs to life after you die, so you keep full ownership of everything during your lifetime. An irrevocable trust is a separate legal entity you create and fund while you’re alive, and once you sign it, the assets generally stop being yours. That single difference drives everything else: taxes, probate, creditor protection, Medicaid eligibility, and cost.
When Each Trust Takes Effect
A testamentary trust exists as instructions inside your will. Nothing moves while you’re alive. When you die, the will goes through probate, the court validates it, and the executor transfers the assets you designated into the newly created trust. Until that probate process finishes, the trust is language on paper.
An irrevocable trust requires a separate trust agreement drafted and signed during your lifetime, plus the actual retitling of assets into the trust’s name. Real estate deeds get re-recorded. Brokerage accounts get re-registered. If you sign the trust document but never fund it, the trust provides none of the benefits people create it for. Funding is where most people stumble.
Control and Flexibility During Your Lifetime
This is the sharpest divide between the two. A testamentary trust gives you unlimited flexibility while you’re alive because it’s just part of your will. Rewrite the will next year and the trust terms change with it. Add beneficiaries, adjust the ages at which children receive distributions, swap trustees, or scrap the trust entirely. You also keep full use of your assets, since nothing leaves your name until after death.
An irrevocable trust locks in its terms the moment you sign and fund it. You generally cannot call your attorney and redirect distributions to a different child or reclaim a rental property you transferred in. That rigidity is exactly what produces the tax and creditor-protection benefits; if you could freely revoke the trust, the IRS and the courts would treat the assets as still yours.
Irrevocable trusts aren’t quite as rigid as the name suggests. A well-drafted agreement can include a limited power of appointment that lets a designated person redirect assets among a group of permissible beneficiaries. Roughly 30 states have trust decanting statutes that allow a trustee to pour assets from an existing irrevocable trust into a new one with updated terms, within fiduciary limits. A court can also modify or terminate the trust if all beneficiaries consent and the change doesn’t undermine the trust’s core purpose. These are not casual workarounds, but they mean “irrevocable” isn’t absolute in every detail.
Estate Tax, Capital Gains, and Ongoing Income Tax
Tax treatment is where the two structures diverge most, and where the wrong choice can be costly.
Estate Tax
Assets in an irrevocable trust are generally excluded from your taxable estate because you no longer own them. For estates above the federal exemption of $15 million per person in 2026, that exclusion can save a substantial amount; the top estate tax rate is 40%.1Office of the Law Revision Counsel. 26 U.S. Code 2010 – Unified Credit Against Estate Tax Married couples can effectively double the threshold through portability, where a surviving spouse claims the deceased spouse’s unused exemption on an estate tax return.2Internal Revenue Service. What’s New — Estate and Gift Tax
Testamentary trust assets are fully included in your estate. They never leave your ownership until death, so they count toward the estate tax threshold like any other probate asset. For most families whose total estate falls well under $15 million, that distinction triggers no federal estate tax at all.
Step-Up in Basis
Here’s the hidden cost of an irrevocable trust that surprises many families. Under federal tax law, assets included in a decedent’s gross estate receive a step-up in basis to fair market value at the date of death.3Office of the Law Revision Counsel. 26 U.S. Code 1014 – Basis of Property Acquired From a Decedent Heirs who later sell owe capital gains tax only on appreciation after the date of death, not on decades of prior growth. Testamentary trust assets always qualify, because they’re part of the estate.
Assets transferred into an irrevocable trust by completed gift during your lifetime generally do not qualify. The IRS confirmed in Revenue Ruling 2023-2 that if trust assets aren’t in the grantor’s gross estate, the step-up doesn’t apply. Beneficiaries inherit your original cost basis and face a larger capital gains bill when they sell. The trade-off is real: remove the asset from your estate to save on estate tax, or keep it in the estate so heirs get the step-up. For highly appreciated real estate or long-held stock, the capital gains hit from a low basis can exceed the estate tax saved.
Ongoing Income Tax
An irrevocable trust that earns income must file its own return on Form 1041 once gross income reaches $600 in a year.4Internal Revenue Service. 2025 Instructions for Form 1041 and Schedules A, B, G, J, and K-1 Trust tax brackets are severely compressed. For 2026, trust income above roughly $16,000 is taxed at the top federal rate of 37%, a threshold individual filers don’t reach until income exceeds $626,000. Undistributed income inside the trust hits the top rate almost immediately, which is why trustees often distribute income to beneficiaries so it’s taxed at their lower personal rates.
A testamentary trust faces the same compressed brackets once it’s funded, but there’s no trust-level income tax to worry about during your lifetime because the trust doesn’t exist yet.
Probate and Privacy
A testamentary trust cannot avoid probate. The will that creates it must be filed with the probate court, validated, and administered under court supervision. The process can take months, and during that time the trust terms, the assets, and the beneficiaries’ names become part of the public record. Some jurisdictions keep testamentary trusts under ongoing court supervision after they’re established, with periodic accountings and additional legal fees over the trust’s life.
An irrevocable trust sidesteps probate entirely. Because you already transferred ownership to the trust during life, those assets aren’t part of the probate estate at death. The trustee keeps managing and distributing assets with no court filing, no public record, and no waiting period. This matters especially for families who value privacy or who own real property in more than one state, which could otherwise trigger a separate probate in each state.
If an estate is small enough to qualify for a state’s simplified probate procedure, the time and cost advantage of avoiding probate shrinks. Thresholds for streamlined processes vary widely by state.
Creditor Protection and Medicaid
Creditor Protection
When you fund an irrevocable trust for someone else’s benefit and include a spendthrift provision, the assets are generally shielded from both your future creditors and the beneficiaries’ creditors. You don’t own the assets anymore, so your creditors can’t reach them, and the spendthrift clause blocks beneficiaries from pledging their interest or having it seized.
There’s a limit. In most states, if you create an irrevocable trust for your own benefit (a self-settled trust), your creditors can still reach the assets. A handful of states permit domestic asset protection trusts that offer self-settled protection, but the majority do not. A testamentary trust offers no creditor protection during your lifetime because the assets never leave your estate. After death, a spendthrift clause can protect beneficiaries from their creditors, but only once the trust is funded.
Medicaid Long-Term Care Planning
Moving assets into an irrevocable trust is a common Medicaid strategy, but timing is everything. Federal law imposes a 60-month look-back period before a Medicaid long-term care application.5Office of the Law Revision Counsel. 42 U.S. Code 1396p – Liens, Adjustments and Recoveries, and Transfers of Assets If you fund an irrevocable trust within that five-year window and then apply, the transfer counts as a disqualifying gift and triggers a penalty period of ineligibility. Transfers made more than 60 months before the application are not penalized.
A testamentary trust provides no Medicaid planning benefit. The assets stay in your name until death, so they’re fully countable for eligibility purposes.
What Each Trust Costs
A testamentary trust is cheaper to create because it’s drafted as part of a will you’re paying for anyway. The real costs arrive later: probate filing fees, executor fees, and attorney fees that in some states run between 3% and 8% of the estate’s value. Ongoing court supervision of the testamentary trust can add further legal costs over time.
An irrevocable trust costs more upfront because the trust agreement is a separate, complex document and the attorney has to handle the asset transfers. Professional trustee fees typically run 1% to 3% of trust assets per year. The trust avoids probate entirely, which for larger estates can more than offset the higher setup and administration costs. Both types of trusts need their own tax returns, which adds annual accounting fees.
Which One Fits Your Situation
For most families with estates well under the $15 million federal exemption, a testamentary trust built into a will handles the most common goal: making sure minor children or vulnerable beneficiaries don’t receive a lump sum they can’t manage. It’s simpler, cheaper to set up, and preserves full flexibility while you’re alive. The step-up in basis for inherited assets is a meaningful tax advantage for heirs who plan to sell.
An irrevocable trust makes more sense when the estate is large enough that estate tax is a real concern, when asset protection from creditors or lawsuits is a priority, or when Medicaid planning requires moving assets out of your name at least five years before you’ll need long-term care. The costs are real. You give up control, you lose the step-up on transferred assets, and you pay more in legal and administrative fees. For the right situation, those costs are small compared to the estate tax saved or the Medicaid eligibility preserved.
The two structures aren’t mutually exclusive. Some estate plans use an irrevocable trust during life to shelter specific high-value assets and a testamentary trust in the will to handle whatever remains at death. An estate planning attorney can model the tax impact of each approach against your actual asset values and family situation.