Is it a mortal sin to get remarried without an annulment?

Answer 1

A Catholic is not free to marry more than one person. The annulment process is simply that: a process which must be investigated to its final verdict on whether or not a previous marriage existed or not. During the time this is being investigated, the Catholic is still to be considered 'married' and thus not eligible to date others, marry someone else, or have marital relations.

If the marriage is found to be in tact, it can not be broken by any man or institution here in this world. Only God can dissolve the bond, at death. As it is written: "For what God has joined, no man may separate." (Mark 10:9)

To violate the marriage covenant is a very serious (mortal) sin. The Church can not be more clear on this: any Catholic that violates this sacred bond of marriage is indeed committing adultery and anyone associating themselves with a married Catholic is also committing adultery.

The Church also goes on to say that marriage is not just a supernatural grace that comes from receiving the sacrament but a natural institution as well. That is, before Jesus' time here in this world, marriage was (and still is) an institution between a man and a woman governed by natural law. This is why the seventh commandment states, "You shall not commit adultery" because it isn't just something that Christians believe. Instead, when it comes down to it, all rational thinking humans deep down really understand marriage as important and adultery as wrong.

Answer 2

Actually, it is impossible to "remarry" without an annulment as you are still validly married. An annulment is just a declaration that no valid marriage was contracted in the first place. To attempt marriage again, without a prior declaration of nullity (an annulment) would indeed be a mortal sin.