The lender launched product transfers in December 2017 and said brokers have consistently asked for this feature.
Additional borrowing will be underwritten prior to the product switch.
Minimum additional borrowing will be set at £10,000 while maximum borrowing is limited to £500,000.
The rates for the additional borrowing will be the same as the product transfer rates and normal new business procuration fees will apply to the additional borrowing.
Graham Felstead, head of intermediary mortgage at NatWest Intermediary Solutions (pictured), said: “I’m delighted we are adding additional borrowing to our product transfer process and believe this further demonstrates our commitment to the market.
“We are constantly reviewing our proposition and product offering, as well as listening to broker feedback to ensure our approach best suits brokers and their customers.”
Santander reduces PT rates
Santander is cutting rates on select five-year fixed rates at 75 per cent loan to value (LTV).
Rates will be reduced between 0.05 per cent and 0.10 per cent.
The lender’s product transfer rates are personalised to each customers, and can be seen on its online mortgage transfer service in the introducer internet.
The lender said there will be no other rate or fee changes, with all charge end dates to roll on by one month.