I would say we do not top slice in the traditional sense. The way it works is if the client has surplus personal income or surplus portfolio rental income this can lower the rental calculation that is used. As an example, if a client is a higher rate taxpayer the rent needs to cover the monthly payment 145% (i.e the rental income needs to be 45% more than the monthly mortgage payment). If there is a surplus portfolio rental income, then the system will look to reduce this coverage to a minimum of 125%.
It is worth noting that if undertaking a client’s personal BTL decision in principle (DIP) the system can take into consideration the client’s personal commitments which can affect affordability. This would only be determined at DIP stage, so I would suggest completing a DIP in this instance.