Dating during a marital separation may or may not classify as cheating, depending on the promises made and expectations held by both spouses.
Having an affair during a temporary, let's-take-a-breather separation is very different than a romantic involvement after a final, legal separation. In either case, however, dating while technically married can have detrimental legal effects in some states.
Expectations and Promises
When the word "cheating" is used in a marriage, it generally implies that one spouse has broken a promise of fidelity. But when does this promise end? The answer varies widely among individuals. For some people, never; and the “till death do us part" vow makes any dating forbidden, even after separation or divorce. Others see marriage as a legal institution that is terminated—together, with all commitments and responsibilities—upon divorce. Still others consider certain types of separations enough to cancel previous marital commitments.
Types of Separations
Whether separation annuls marriage vows in a moral sense may depend on the type of separation in question. Marital separation means that a couple is living apart, but the range of categories that fall within this classification is great. Some couples decide to live apart for a few months while working on their issues. Other times, spouses separate when one moves out and files for divorce. Married couples may go to court and obtain a legal separation, with a court decree resolving all custody, support, and property issues—the equivalent of a divorce in all but name.
Evaluating Your Separation Commitments
To decide whether your actions constitute cheating, morally speaking, you'll have to review the terms of your separation. If you and your spouse agreed not to see anyone during this period, dating is cheating. If nothing was said about the subject, but you and your spouse are actively working on your marriage during this phase of your relationship, a promise to not be intimate with a third party can be implied.
A "break" is not a break-up, according to psychologist Mark White, and dating around violates the spirit of your arrangement.
Years ago, having an affair while still in a marriage constituted adultery and provided grounds for divorce. All states now provide for no-fault divorce, and in some—like California—adultery cannot be considered in property division or support awards either. However, this doesn't always mean that adultery has no effect on your divorce. The majority of states also permit fault-based divorce on grounds, including adultery. If your spouse wins a divorce based on your adultery, it may affect the division of marital property, as well as alimony rights.
As you can see, the definition of “cheating” has many definitions and variations based upon circumstances and basic understandings—implicit or explicit—between couples. One cannot make claims as to what is right and not right, but it's safe to say there should be a mutual agreement between the individuals involved.