Around 350,000 homeowners move each year while carrying an existing mortgage. The process is more involved than a first purchase because you are simultaneously selling, buying, and managing your existing deal.\n\nPorting Your Mortgage — If you have a good fixed rate with time remaining, porting saves thousands. Not all products are portable. Even if portable, you must pass current affordability at the new amount. If buying more expensive, you can port and take additional borrowing at the current rate.\n\nThe Property Chain — A chain exists when multiple transactions are linked. If any link breaks, the entire chain can collapse. Average chain length is three to four transactions. Chains are the single biggest cause of failed sales.\n\nBreaking the Chain — Sell first and rent temporarily (costly but gives certainty and makes you chain-free). Use a bridging loan to buy before selling (expensive but removes dependency). Accept a lower offer from a chain-free buyer.\n\nTiming Completion — Ideally sale and purchase complete on the same day. Your solicitor coordinates with all parties. If completions happen on different days, you may need temporary bridging or accommodation.\n\nEarly Repayment Charges — Leaving a fixed deal without porting triggers ERCs. On 200,000 at 3% ERC, that is 6,000. If your deal expires within months, waiting avoids the charge.\n\nCosts of Moving — Estate agent fees (1% to 2% plus VAT), solicitor (1,000 to 2,500), stamp duty, removal costs (500 to 2,000), mortgage fees, survey costs, and a 2,000 to 3,000 contingency.