Interim valuation in construction, typically a manual, time-intensive process, verifies the contractor's work for payment (RICS, 2015). This process is essential for issuing interim certificates in construction projects with a duration of more than 45 days in the UK. Recent advances in generative AI (GAI) have spurred automation in construction and created opportunities to enhance business productivity. Thus, IVP manual and software processes which have not led to significant gains in construction productivity can explore the potential of GAI. Lack of automation in interim valuation and payment practices contributes to errors, productivity loss, and over 75% of UK contractors experiencing payment delays (Kolleno, 2023). UK construction disputes are mainly influenced by payment issues, which have spiked by 117% in 2020\. This has cost the UK construction sector an extra £27.7 million (PBC Today, 2023). These numbers are increasing because of project complexity and the absence of stakeholder involvement in decision-making. Automating interim valuations through machine learning, alongside stakeholder-centred design, can support stakeholder satisfaction and delivery. IVP automation through extended reality, such as virtual reality and augmented reality, can support data direct data capture from construction sites for foundational language models (FLM), leading to GAI development for quantity surveying services. A combination of Mixed Reality (MR) and Generative AI has significant potential for cost-saving and efficient project delivery. Unlike Virtual Reality (VR) and Augmented Reality (AR), MR combines AR and VR, allowing users to interact with digital and real physical elements simultaneously. Productivity of quantity surveying (QS) services through GAI with continuous improvement measures of MR historic and on-site data will reduce repetitive administrative tasks by at least 35% within 3 months of usage. This will be facilitated through direct prompting options for IVP and payment issuance to contractors. The accuracy of cost-value reconciliations, IVP and final accounts as a faster output will encourage competitive advantage. This feasibility study will design, integrate and validate a pilot QS-GAI application for interim valuation and insurance of payment notices to contractors through prompting. A commercialisation and exploitation plan for advancing the feature of QS-GAI will ensure the inclusion of a payment gateway, FLM expansion into LLM and the addition of new quality assurance features through continuous data capture.