My daughter's British passport expires in December, can I renew it in?
It takes up to ten weeks for the new passport to be issued. In addition, some countries require that there is at least six months left on the passport. If you are going to one of these, you will need to apply nine months before you leave. Unfortunately, the unexpired time on the old passport is not added to the new one so there is a disincentive to renewing too early.