The UK has a target to reach net zero carbon emissions by 2050\. Heat networks -- where heat and hot water is provided to many properties from a shared energy source (also sometimes called district or communal heating) - will be a critical part of this: they currently provide 2-3% of all heat in the UK but this will have to rise to around 18% if the UK is to meet its carbon targets cost effectively. This will require a drastic improvement in knowledge and current network performance: one way to support this is to improve the use of data in a data-rich sector. Poorly managed heat networks lead to poor system efficiency and increased carbon emissions. When operated and maintained well, these networks are an ideal solution to provide low cost, low carbon and low hassle heat and hot water to the end-user and be 'headache-free' to the heat network operator. Without heat network measurement, there will be no improvement and their net zero promises will not be met. There is currently no data to enable the benchmarking and comparison of the UK's heat network fleet to drive net zero: it's a serious data gap. Our innovation is simple. HeatMark will provide clear data on heat network performance for a scheme, across a portfolio and across the sector. It will build the data and analysis needed to allow heat network managers to assess and improve scheme performance, saving both carbon and customer costs. And with full regulation on the horizon, HeatMark will also provide regulators and policy makers the evidence to shape the future of heat networks to ensure they play their part in the net zero future. As well as using existing data, HeatMark will also deploy and test Internet of Things (IOT) monitors on existing heat networks with no or limited monitoring; an affordable, unintrusive and quick way to obtain the data for benchmarking using an innovative technology that is proven in other sectors but not yet widely deployed on heat networks. HeatMark will become a powerful tool for the sector, for regulators, policy makers and for customers in lower carbon, more efficient and lower cost heating and hot water in the UK. It will allow heat network operators to bring their systems in-line with industry standards, promote the decarbonisation and efficient delivery of heat, and bring reliable, affordable heat and hot water to customers.