The probate process is the process by which an estate is administered and property is transferred to the beneficiaries of the estate. If there is a will, the person who has died (often called the "decedent") is said to have died testate, and if there is no will, the person is said to have died intestate.
The length of the probate process is not affected by whether or not one has a will, but whether or not the decedent had a will does affect those to whom notice must be given. If one has a will, the beneficiaries who take under the will (called "devisees") must be given certain notice as described in further detail below. In all cases, the decedent's "heirs" (a defined term that means those who would take under the laws of intestacy) must be given notice. If all of a person's assets are non-probate assets (see this page for additional details on whether property is probate or non-probate), the probate process can be avoided altogether. If the decedent has no probate real property and less than $25,000 in personal property (including bank accounts), then there is a shortened version of probate that is both quicker and simpler.
For the "long form" of probate, the process starts by filing an Application or Petition with the probate court in the county in which the decedent resided. Once a Personal Representative (what previously was called an "executor") is appointed, they have 30 days to send an Information to Heirs and Devisees to the devisees (those beneficiaries specified in the will) and the decedent's heirs (who may not necessarily be the same people). Notice must also be published in the newspaper for the county so as to notify creditors of the decedent that they should file a claim with the probate court. In most counties, the probate court will do this for the Personal Representative.
Within 90 days of appointment, the Personal Representative must file and Inventory and Appraisement listing all of the decedent's probate property. Note that it is only the probate property that must be listed on this form. The probate fee (approximately 0.25% or $250 per $100,000) is calculated based on the Inventory and Appraisement form.
Once these forms are filed, there is a lull in activity. Creditors whose claims arose before the decedent's death (such as medical bills and credit card bills) have eight months from publication of notice to file a claim against the estate. During this time, if no creditors file any claims, the Personal Representative has very little to do other than manage the assets of the estate and prepare for distribution. Because creditors are barred from filing claims against an estate (for claims arising before death) after the decedent has been dead for one year, if probate is opened significantly after the decedent's death, the Personal Representative may proceed with closing the estate before the eight month creditors' period has passed. This is because the one-year-from-death period passes before the eight-month-from-publication period does.
Once the eight-month or one-year period has expired, the Personal Representative can commence closing the estate. Closing the estate can be a very simple or very complicated process depending on whether the beneficiaries are willing to cooperate with the Personal Representative. Assuming there is no cooperation (which is rare), the Personal Representative must file a Final Accounting, Proposal for Distribution, and Notice of Right to Demand a Hearing with the probate court and then send those documents to the beneficiaries. This is quite a burdensome process because the Final Accounting requires a complete accounting of the receipts and expenses (called disbursements) of the estate.
If the beneficiaries are willing to waive the forms mentioned above, they may execute the Waiver of Statutory Filing Requirements waiving the Final Accounting, Proposal for Distribution, and Notice of Right to Demand a Hearing. While they are not required to execute this form, it dramatically reduces the complexity of the estate and the costs of administration. Although distributions can be made at any time, because the Personal Representative could face personal liability for distributing the assets too early, distribution of the assets should almost always be a Personal Representative's final act (other than filing the necessary tax returns).
As you can see, the length of time probate can take is dependent upon two major factors: (1) the type and amount of probate assets, and (2) when the probate process is begun. If there are no probate assets or no probate real property and less than $25,000 total probate property, then the process can be accomplished in a matter of weeks. If the longer version of probate is required, then the length of time the process will take will depend on whether or not the Personal Representative is required to wait for the eight-month creditors' claims period to expire.