For purposes of marital fault, only conduct which occurred prior to the date of separation can be used as marital fault. However, if one spouse can prove the other had a romantic relationship with a third party before date of separation, their activity after the date of separation can be used for corroborative purposes.
Generally, it is a good idea to wait at least three months after separation to start dating. If you enter into a new relationship immediately after separation, it just invites the other spouse to assume something was going on before you separated – even if that is not the case. Be aware, however, adultery is still a statutory misdemeanor in North Carolina for any married person who has extra-marital sex. Despite that, the district attorney’s office generally has no interest in criminal prosecution of this statute.