The agreement or statement of work that defines the new scope, and a fresh support letter from the engaging entity describing it. Where the change is material, those documents support a new application rather than an amendment of the old one. The credential evidence does not change and does not need reissuing.
New facts need new paper, not annotated old paper
The instinct when an engagement grows is to email a variation and carry on. That works commercially and does not work here, because the file that supported admission described a particular scope for a particular period. If the scope has genuinely changed, three documents need to exist in their new form.
First, the agreement or statement of work, signed, showing what will now be done and until when. Second, a letter from the engaging entity describing the work in its own words and confirming the contracting relationship. Third, where the engaging entity itself has changed, evidence of which company it is, because groups often reassign contracts between subsidiaries without telling anyone.
The credential documents are static: the degree, the transcript, or the experience letters supporting the five-year alternative. Those are produced again but not rewritten. The judgement call is whether the change is material enough to need a new admission, and that should be taken before the new work starts, not after.