The Department and HS2 Ltd still disagree on the estimated total costs for completing the programme. Despite using the same data, the Department and HS2 Ltd told us that estimates differ because they disagree over a range of technical factors relating to the methodology used for the estimates and assumptions used, for example over the value of remaining risks on the programme and productivity savings.16 HS2 Ltd also had limited cost information from the supply chain, which reduced its ability to assess which cost increases were necessary.17