If a decedent (person who is deceased) has real property or tangible personal property in a state other than the state where the decedent lived at the time of death (primary residence or domicile), an ancillary probate proceeding in the other state where the property is located will probably be necessary to transfer title to the property—unless, for example, the decedent took steps to transfer title to the property before death. After the domiciliary probate process is initiated in the state of the decedent’s primary residence, the executor or administrator of the estate may open an ancillary probate proceeding in the state where the property is located.

The ancillary probate is usually an abbreviated process that relies in whole or in part on the domiciliary probate court’s admission or acceptance of the will for probate. Thus, any challenges to the validity of the will generally must be made in the domiciliary probate court. And once the domiciliary probate court admits the will to probate and grants the executor or administrator authority to act on behalf of the estate (letters testamentary, letters of administration), the executor may file a copy of the will and the letters testamentary or letters of administration in the ancillary probate court. The ancillary probate court will then admit the will to probate in that state as a foreign will, giving the executor or administrator the authority to transfer or sell the property in the ancillary probate state.

In California, if a decedent owned real property or tangible personal property in a state other than their primary residence at the time of death, an ancillary probate proceeding may be necessary in the other state to transfer the property title. This is typically required when the decedent did not arrange for the transfer of the property title before death. The ancillary probate process is generally more streamlined than the initial probate process and relies on the primary probate court's decisions. Challenges to the will's validity are usually addressed in the primary probate court. Once the will is admitted to probate and the executor or administrator is granted authority (through letters testamentary or letters of administration), these documents can be filed in the ancillary probate court. The ancillary court will recognize the will as a foreign will, allowing the executor or administrator to manage the property in that state.