As well as Comma
The phrase as well as creates one of those situations where you may have to make a judgment call about comma usage. As a general rule, it doesn’t need a comma before it unless it’s a part of a non-restrictive clause.
Please proofread for spelling mistakes, as well as grammatical errors.
This sentence doesn’t require a comma.
Spelling mistakes, as well as grammatical errors, are distracting to a reader.
This sentence does require the commas around the non-restrictive clause.
I like carrot cake, as well as chocolate cake.
I like carrot cake as well as chocolate cake.
Both sentences clearly mean that I like both kinds of cake; the comma use is probably not necessary. We’d probably only use the comma in the second sentence if we were writing dialogue and wanted to show where the speaker paused.
I like carrot cake as well as chocolate cake, but lemon cake is my favourite.
This sentence doesn’t need a comma in front of as well as; the meaning is quite clear.
I don’t like carrot cake as well as chocolate cake.
I don’t like carrot cake, as well as chocolate cake.
These sentences clearly demonstrate where a judgment call is required. The first sentence means that I prefer chocolate cake. The second sentence means that I don’t like either of them.