TSB has increased the maximum age allowed for buy-to-let mortgages from 75 to 80.

The lender has also updated the way it calculates affordability for landlords.

For a buy-to-let loan to be considered affordable, the annual rental income must be more than 145 per cent of the annual mortgage interest. 

However, the way that it calculates annual mortgage interest has changed.

The interest calculation was previously based on the higher of either the pay rate plus 2 per cent, or 5.5 per cent, regardless of application type.

The affordability calculation has now changed to the following:

Now for remortgages with no additional borrowing it will use the higher of either 4.5 per cent or the pay rate plus 1 per cent, no matter what length of fixed rate the landlord chooses.

For all other buy-to-let applications it will use the following calculations:

• Where the landlord is fixing for less than five years it will use the higher of either 5.5 per cent or the product rate plus 2 per cent.
• Where the landlord is fixing for five years or more it will use the higher of either 4.5 per cent or the product rate plus 1 per cent.