A Pre-Underwritten file is the strongest of the “pre’s”. This type of approval is more in depth and has a higher likelihood of being closed. The lender, when working with you, will go in depth on your application. Just like the pre-approval, they will/may ask for all your assets information, your income for the past two months, possibly tax returns and any other information need to approve your application. This in turn is sent to the underwriting team and given a conditional approval. The conditional part is usually the property type and appraisal.
This type of qualification is the best but can also take a bit more time to accomplish in a fast paced market.