Here are the most common reasons for a buy to let mortgage to be declined:
The application hasn't been filled out correctly: Make sure you know exactly what is required and put together a checklist, so you don't miss anything.
Rental income doesn't add up: Lenders will require the rental income to exceed the monthly repayment amount by 25% and 45% and typically assume an interest rate of 5.5%.
You're too leveraged as a portfolio landlord: If you have 4 or more properties, you'll be classed as a 'portfolio landlord.'
You've exceeded the maximum amount of buy to let mortgages: Most lenders will have a maximum amount of borrowing they'll allow one person to have.
A lower valuation on the property you wish to buy: The lender may reject the application if the surveyor puts a lower valuation than the agreed purchase price.