If these are not correct, why? What do they mean?
1. You can do that next year. (Is 'the' ommitted in this sentence?)
2. You can do that the next year. (I don't hear a lot of people say this.)
3. You can do it next year.
4. You can do it the next year.
The phrase next year means the year following this one. The the is contained within the definition of the phrase.