NatWest will increase its total number of buy-to-let properties landlord customers can own from four to 10 on Wednesday.
The total will include unencumbered properties and properties mortgaged with NatWest and another lender.
It is also increasing its maximum aggregate customer borrowing allowed to £3.5m, up from 2m.
The current £50,000 minimum income for aggregated borrowing over £1m will be removed. All customers will be required to meet the standard buy-to-let minimum income of £25,000.
Sarah Taylor, service development manager NatWest Intermediary Solutions, said: “This important step will simplify our buy-to-let policies and means we can be there for a wider customer range in what is a growing market.”