NatWest Intermediary Solutions will be introducing a 4.99 times loan-to-income cap per application for all buy-to-let business on Monday 14 July.
This will mean it will mirror the rest of the RBS and NatWest mortgage channels.
This change of policy is being introduced to create greater consistency between buy-to-let and residential lending policy, the lender said.
The maximum LTV for buy-to-let mortgages remains at 75% as does the maximum loan size of £500,000. All other remaining criteria remain unchanged.
The new policy will also be introduced on the same date to buy-to-let mortgages from RBS Intermediary Partners and RBS and NatWest mortgages available through the retail channels.