As a client recently noted, many people think Wills are self-executing: That after a person dies, all their beneficiaries have to do is follow the instructions in their Will. That's not quite the case. A probate proceeding ensures the proper person is appointed executor and that the deceased person's possessions are organized, creditors paid, and gifts passed on to beneficiaries.
(Originally "probate" referred to the court process by which Wills were proven to be valid, but American probate courts have the power to manage estates whether the decedent executed a Will or not.)
In a probate proceeding, a person asks to be appointed to manage the decedent's affairs. A court commissioner or judge will evaluate whether that person is the right person. Were they nominated in a Will? Are they close family? Or is it a creditor? Does anyone object to the appointment? Is the requester a felon? If the court approves the appointment, the person becomes executor of the estate. They then must follow Washington's very specific probate rules. In some situations, the court might give the person fairly free rein to manage the estate; in other cases the court might want to closely supervise each step.
In Washington, a probate is necessary if the decedent owned real estate in the state, or if they had assets worth more than $100,000 (not including some assets that automatically transfer at death). There are a few situations in which no probate is necessary after a death. For example, if a married couple signed a Community Property Agreement, after the first death the entire estate passes to the surviving spouse - even real estate. Or, if a decedent's only assets were money in bank accounts that were co-owned with a loved one, those bank accounts would transfer automatically to the co-owner without probate. Similarly, no probate may be necessary if the decedent's assets all were held in a trust.
When people die owning less than $100,000 and no real estate, Washington law allows a family member to claim and distribute their assets without going to court to open a probate. The process for claiming those assets is described in state law at RCW 11.62.010. In short, the claiming family member must draft an affidavit to present to the bank, or employer, or whoever else is holding the decedent's assets. They must also provide it to the State of Washington - which might send the claiming family member a bill for the decedent's debts.