Does a pre-approval guarantee a loan?

Having a preapproval approved is just an indication that a lender feels like you have a suitable financial position. However, it isn’t a guarantee that they will formally approve your loan. They need to make sure the security is suitable and they will still need to do a more thorough assessment of your financial position in full to determine how much they will lend to you.

Even if you have a preapproval a lender may not approve a home loan if your financial position has changed (ie. You have lost your job or your work hours are reduced), maybe you have switched jobs or your credit score has changed (you have taken out a new credit card or personal loan etc.).