A lot of businesses offers Estimates under a certain currency while clients prefer to pay using a different currency. It messes up our accounting records because I have to go all the way from deleting the accepted estimate and sent invoice to the client before I could change one invoice and enter payment using the correct currency used. What if they decide to move to a different country next year and they opt to use a different currency? It means I cannot issue a new estimate/invoice under a new one, wherein as your team suggested to make a multiple contact, so what happens to it being sync?