Christina and Wayne have posted an update on their collected Addenda and Corrigenda for their works on/about Tolkien. ... addenda-and-corrigenda-2/

With the release of the new three volume edition of the Companion and Guide, they have stopped updating the A&C for the two volume edition and only are posting updates for the new edition.

I have greatly enjoyed both editions, and have many dozens of post-it notes stuck in the new three volume edition for some research I am currently working on. It is well worth the investment, and well discounted at this time from various online retailers ( link below).