NEC3 ECC: Is documentation after or before Completion?

Should terminal float comes after site works completion date or documentation planned completion

Terminal float is the difference between planned Completion and Completion Date. It depends therefore on your definition of Completion. If it is a requirement to have your documentation in place in order to achieve Completion, then your planned Completion (and hence terminal float) would be after that documentation. If the documentation is not required as part of WI and if the Employer does not need it in order to be putting the works into use, then planned Completion (and hence start of terminal float) could be before the documentation is in place. I would suggest that most documentation would probably be needed for them to be using it safely etc. so in most instances it is probably the former rather than the latter.