The way I see it is: BS7671 states that a periodic inspection notice must be applied to an installation on initial verification and updated on each periodic inspection.
Therefore the addition of a circuit is not the initial verification of an installation nor a periodic inspection therefore a periodic inspection notice is not required to be supplied and any existing notice should not be updated.
In the case where there is no notice present and a new circuit has been installed then it should be noted in the condition of the existing installation - no periodic notice is present.
In the checklist there is no requirement under the work you are doing to provide a periodic notice and so the tick box should be marked N/A.
I would say though that I do tend to tick the box if a notice is present (hmm, not very often in domestic), I must train myself out of assuming the tick list should be completely filled in no matter what you are doing, the check list only applies to the work you are doing and anything not applicable to that work should be N/A, you do not need to check it, verify it or tick it.