In short, this depends on the bank, talk to the most senior person you can, ideally someone in collections or recoveries, some banks will allow you to carry the shortfall unsecured at a preferred rate for a long term, lets face it, its better that a mortgage in default. Each case is usually assessed on its own merits, send in the request in writing before you call and include income and expenditure details and a statement of affairs ie all assets and liabilities. If you have savings, they will want you to set these against the shortfall. Some institutions are doing this especially with buy to lets, others are not there yet. Who's you're bank?