A separate will that governs specific assets — most often shares of a private corporation — alongside a primary will that covers the rest of the estate. Business owners use a secondary will to keep private-company shares out of the probated estate, which can reduce probate fees (since those fees are typically based on the value passing through probate) and allow the shares to transfer to a chosen successor quickly, without the delay probate of the main estate can cause.
The primary and secondary wills must be drafted to dovetail, each clearly governing its own assets, to avoid conflict or overlap. A secondary will is a common element of business succession planning.