The statute of limitations in North Carolina for breach of contract is four years. With something like monthly dues, the statute resets each time that a payment is missed, but the board could never go back more than four years prior to the date that they filed a lawsuit.
Now, that assumes that (1) the common assessments are authorized by the declaration and bylaws (which they usually would be) and (2) that someone, at some point, communicated the amounts due. If the bylaws simply say that the HOA has the ability to assess common fees, and no fees were ever assessed, there isn't a legal basis for going back in time to impose fees.
If unit owners were spending their own money to maintain common areas because the board was not doing so, they may have a counterclaim for the monies spent, because the HOA has a legal obligation to do maintenance
and repairs. They cannot refuse to do the work, force the owners to do it themselves, then collect money for work they never did.
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