This depends on the type of mortgage rate you have and who your lender is, but you may be able to take this mortgage with you to your new home, this is called porting. If you are buying a house that is more expensive and you need additional borrowing, then subject to the lender approval you can take your existing mortgage to the new home and ‘top up’ with additional borrowing. You would end up with 2 mortgage rates on your account, your existing rate and a new rate. If you were purchasing a cheaper property and wanted to repay some of your existing mortgage, then this is also an option within certain limits. Your existing mortgage offer document is a valuable source of some of this information.