Q. I have seen my very busy neighbor arrive home by car past candle lighting time is it permitted to drive at this time, if so until when may one drive after candle lighting time?
Similar question: Do I have to tell my neighbor that he is driving late Erev Shabbath close to sunset and he is giving a bad example and making a chilul Hashem? Or should I ignore, since I may get into a fight and eventually not solve anything, just creating a machloketh? What is best and right?

A. Igrois Moshe (O,H. 1: 96) explains that men do not automatically accept Shabbos at candle lighting time; usually there is still eighteen minutes between that time and sunset. Since this is a well known fact, there is no prohibition of maaras ayin or concern that others may think one is desecrating Shabbos.
Horav Shlomo Miller’s Shlit’a opinion is that you have to deduct about two minutes from the time of the shekiah, since the times are not necessarily exact to the minute. Also some time should be left for complying with the mitzva of Tosefes Shabbos adding a few more minutes.
That is not to say that it is proper or advisable to travel or do melochos so close to Shabbos, but it is not prohibited.
It is better to have the Rabbi of the shul the neighbor attends deal with the issue, to avoid ending in an unnecessary machlokes. (See also question 1452).

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a