The Declared Value (DV) is the full reinstatement value which is calculated by your surveyor conducting the RCA. The DV is the figure presented in the RCA report. The Sum Insured (SI) is set by the insurer for the building, not the surveyor. The SI is the DV plus a provision for inflation which is typically 20% to 50% of the DV. For instance, a DV of £5,000,000 as calculated by your RCA surveyor would become an SI figure of £6,500,000 after a 30% uplift as applied by the insurer. For the purposes of an RCA, you only need to think about the DV.