From NASA
Where do we consider our solar system to end; Pluto's orbit? Solar apex?
The solar system may be broadly defined as consisting of all those objects that are ultimately governed by the gravitational field of the sun. In addition to the planets, moons, asteroids and dust of the planetary system, it includes the distant bodies of the Kuiper Belt and Oort cloud, the last extending perhaps as far as 50,000 astronomical units (1 AU = about 93 million miles). The gravitational influence of the sun may extend as far as 2 light years. (From "Solar System", James H. Shirley, in Encyclopedia of Planetary Science).
https://voyager.jpl.nasa.gov/frequently-asked-questions/