Do you always have to be married a year before you get sealed in a second marriage?

No.

It does depend on what your local laws are.

If you're both temple recommend holders, before you're married, you can do both ceremonies the same day. In some places the church insists they happen within a week of each other. The church wishes the couple to remain chaste until after the temple wedding.

In many places, the temple marriage counts as a civil marriage as well.

The situation of waiting a year before a temple marriage, is to give both members of the couple time to be temple recommend worthy before entering the temple. New members are required to wait a year before entering. And civilly married couples, who were intimate before their temple wedding are normally required to wait a year before going back Rio the temple. If that makes sense.

Results may vary.

/r/latterdaysaints Thread