In 2010 a two member LLC filed form 2553 with the IRS to request to be taxed as an S Corp. The IRS granted permission and the co has filed form 1120-S since that time. Effective January 1, 2017 one member sold his equity interest to the other member. Thus the 1120S tax return that will be filed next year covering year 2017 will be on behalf of the remaining sole member only.

Is is necessary or required that the IRS be notified in advance of filing the return for year 2017, of the change in ownership which was effective January 1, 2017?

Please advise. Thanks

Given that you have asked about this LLC 3 times over the last month, I think it's time that you research irs.gov instead of asking people to do it for you for free.
It does appear that you consult to small businesses for a living.