Open market rent is the amount a willing landlord and a willing tenant would agree on for a property, on the open market, on the date the rent is being assessed. It assumes both parties are acting freely and reasonably, the property is being let on standard terms, and neither side is under unusual pressure to agree a deal. In short: what the property would actually let for today, if you put it back on the market.

Under the Renters' Rights Act, a tenant who challenges a Section 13 notice can have the rent set at  or below  the figure you proposed, but never above it. That makes proving an accurate open market rent more important than it has ever been for UK landlords.

The calculator looks at recent advertised and let rents for comparable properties in the same area, then adjusts the figure based on the details you enter - postcode, number of bedrooms, property type and condition. The result is an indicative open market rent: a reasonable starting point for pricing a new let or reviewing the rent on an existing tenancy. It's designed to give you a quick benchmark, not a formal valuation.

The rent checker has been built with Section 13 evidence in mind. The estimate is based on comparable local listings and recent lets, which are exactly the kind of data points a First-tier Tribunal looks for when assessing open market rent. Save or screenshot your result alongside the underlying comparables so you have a clear, time-stamped record to support the figure in your Form 4A.