But, it says TN-C-S on the previous EICR.

I've seen that a few times now. My guess was (as Mike suggested) it's just acknowledging DNO advise that any DNO supplied earth terminal should be treated as if it were PME/TN-C-S (which most do these days). There's nothing in the definitions of TN-C-S to say that the N-PE has to be in the consumer's cut-out - there's merely a common convention. The N-PE link could be in the building incomer position (with the consumer's cut-out some distance a way in a flat for instance), or in a DNO feeder pillar outside that then supplies several consumers in the same overall building, or more often, the N-PE link is buried under a pavement somewhere where a joint has been added or a section of damaged cable replaced. Unless N and PE are completely separated all the way back to the substation it can't, by definition, be TN-S and thus it must be TN-C-S (if not TT).

   - Andy.

But, it says TN-C-S on the previous EICR.

I've seen that a few times now. My guess was (as Mike suggested) it's just acknowledging DNO advise that any DNO supplied earth terminal should be treated as if it were PME/TN-C-S (which most do these days). There's nothing in the definitions of TN-C-S to say that the N-PE has to be in the consumer's cut-out - there's merely a common convention. The N-PE link could be in the building incomer position (with the consumer's cut-out some distance a way in a flat for instance), or in a DNO feeder pillar outside that then supplies several consumers in the same overall building, or more often, the N-PE link is buried under a pavement somewhere where a joint has been added or a section of damaged cable replaced. Unless N and PE are completely separated all the way back to the substation it can't, by definition, be TN-S and thus it must be TN-C-S (if not TT).

   - Andy.