A last will and testament is a legal document that contains instructions about who gets your belongings when you die and lets you choose a guardian for a minor child. A will is the first step to creating a solid estate plan, which can also include a power of attorney, an advance directive, and a living trust. You need a will in Washington state to make sure the court doesn't determine your heirs according to state law.
Requirements of a valid will in Washington
Every state has guidelines for a valid will, usually pertaining to the person writing the will (the testator) and how the will is constructed and executed. An invalid will won’t pass muster in probate and will prove a headache to your loved ones after you’ve died.
Anyone who is at least 18 years old can write a will in Washington if they are of “sound mind,” which is called testamentary capacity. (§11-12-010) 
The testator can appoint an executor in the will who will carry out its terms and manage the estate. The executor must be at least 18 years old and cannot have been convicted of felony or crime of "moral turpitude.” Out-of-state executors are allowed but may need an in-state resident to act as a processing agent and receive paperwork. (§11-36-010)
Every will must be signed by two witnesses in the physical (or electronic, starting January 1, 2022) presence of the testator . Witnesses can be beneficiaries of the will in Washington, but unless there are two disinterested witnesses, they may have to forfeit part or all their inheritance since an interested witness creates the presumption that they may have had undue influence on the testator or committed fraud. (§11-12-160)
Can I write a will on my own?
You can make a will without a lawyer in Washington, as long as it follows the requirements set out by state law. Many people use an online will-making service since it’s often cheaper than an estate attorney who can charge as much as hundreds or thousands of dollars to prepare your will, and the cost could be higher in the city than it would be in a smaller town. However, you may benefit from hiring a lawyer to draft your will if you have a complex estate or many assets.
Is a handwritten will legal in Washington?
Handwritten wills are only valid in Washington state if they are properly signed and witnessed. Washington does not allow for holographic wills — wills you write by hand but don’t have witnessed — but the court may recognize those made in another state that allows for them.
Are oral wills legal in Washington?
Spoken wills, called nuncupative wills, are accepted in Washington under limited circumstance to give away personal property up to $1,000 for testators who are members of the armed forces or merchant mariners employed by the US. (§11-12-025)
Electronic wills in Washington
Starting Jan. 1, 2022 Washington law will recognize electronic wills, or wills that are created and executed electronically. For example, you can have your will witnessed over video call. (§11-12-440 and 491)
Do Washington wills have to be notarized?
You do not need to notarize a will in order for it to be valid in Washington. Notarization cannot take the place of proper witnessing outlined above.
After you die, at least one witness must appear in court to verify your will, but you can include a self-proving affidavit to prevent this from happening and greatly ease the probate process after you've passed away. The affidavit must be notarized; you’ll have to pay a small notary fee. (§11-20-020)
Filing the will in Washington
After the testator dies, anyone with the will must file the will with the court or the executor within 30 days. The executor must file the will at the superior court in the county where the decedent lived within 40 days of knowledge of the testator's death. (§11-20-010)
Dying without a will in Washington
When someone dies without a will, the court will determine who receives assets based on state intestacy law, and those heirs may not be who you would’ve wanted. To prevent that from happening, you need to create an estate plan and include a will.
In Washington, a community property state, a surviving spouse is entitled to receive the decedent’s share of marital property (community property).
The surviving spouse is also entitled to inherit some of the deceased’s separate property as well, according to Washington state intestacy law, and this is how much they would receive in a few different circumstances (§11-04-015):
If the decedent is survived by a spouse and:
Surviving spouse's share of separate property
No children, parents or siblings
1/2 of the separate property
No children, but parents or siblings
3/4 of the separate property
Otherwise, when there is no surviving spouse, then the intestate estate will pass along to next of kin in the following order:
Siblings or their children (nieces/nephews)
Aunts/uncles or their children (cousins)