Failure to complete breaches the contract and can bring significant penalties. This will usually include forfeiting the 10% deposit and any other fees paid out. Such situations are very rare, they can be costly to the buyer that doesn’t complete, and you would be advised to take advice from your solicitor regarding any other consequential claims that could be made against you and what other obligations you might have. Buyers in this predicament may wish to explore the possibilities of short term finance and put in place a plan to resell the property quickly after completion.
If you find yourself in this situation, please discuss this with your solicitor and the auctions team.