My partner and I recently purchased a house. We split all expenses related to that purchase (down payment, homeowner's insurance, inspection costs, etc) exactly 50/50. Both of our names are on the mortgage, however since I handled the application, paperwork, communication, etc, my partner transferred her portion of these payments to me, and I paid them out of my accounts.
Going forward, we will also be splitting the mortgage payment exactly 50/50.
We have been together for years and plan to marry this summer, however it's always possible that one of us gets hit on the head, becomes a vindictive jerk, and tries to take the house away from the other.
What can we do now to clearly and definitively document the fact that we have split the mortgage 50/50, so that in case we eventually separate, it's clear that we should each receive an equal portion from the sale of the house?