The NEC3 ECC states you use the Accepted Programme [clause 63.3] which is a defined term that means the latest programme accepted by the PM [clause 11.2(1)]. There's a good article on this subject here:
https://www.builtintelligence.com/blogs/home/54348869-assessing-compensation-events-taking-account-of-changes-since-the-programme-was-accepted
To overcome the NEC3 issues the NEC4 ECC states you use the Accepted Programme current at the dividing date [clause 63.5] and explains how you establish the dividing date [clause 63.1]. Check your contract carefully as NEC released an amendment in January 2019 which changes this clause to add further clarity.
https://www.builtintelligence.com/blogs/home/54348869-assessing-compensation-events-taking-account-of-changes-since-the-programme-was-accepted
To overcome the NEC3 issues the NEC4 ECC states you use the Accepted Programme current at the dividing date [clause 63.5] and explains how you establish the dividing date [clause 63.1]. Check your contract carefully as NEC released an amendment in January 2019 which changes this clause to add further clarity.