A home security system, like a satellite dish or wall-mounted television, belongs to the home seller, who can choose to include it with the home or make it an optional item. Home sellers not working with a real estate agent must give potential buyers a detailed list of the items that go with the home.
In an article for "The Washington Post," real estate attorney Harvey Jacobs writes that what conveys with a home depends on what's customary in the region. The home seller should ask his real estate agent to find out how other home sellers in the area handle built-in security systems. A buyer and seller can also negotiate whether to uninstall or leave the security system in the sales contract.
A home buyer generally conducts a pre-closing walk-through to confirm that the seller has not removed items that come with the home. While leaving the security system behind unannounced might not hurt, a home seller could be sued for breach of contract if she uninstalls the security system after giving the buyer the impression that the system conveys.