Just when I thought I had it figured, there was a new twist to the tale...
The Client Code (NZCS 2240 came through without fuss.
Then the parcel was marked "held for clearance" on NZPost tracking. So I phoned NZ Customs. Nope, I didn't need the Client Code! I was told to phone NZPost 0800 478-287 option 2...
There I was given the entry invoice number and advised to pay $357 online at Pay.Customs.govt.nz so off there to pay...
First I entered entry number and the exact amount advised was reassuringly displayed.
Following through with payment, I was advised an extra ($9) was added for bank fee.
So back to keeping an eye on tracking. As it turned out, the parcel was released shortly after though tracking delayed the status about 12 hours.
As a side note, written advice of the parcel held for clearance was subsequently received so I didn't have to do any phoning though the process was sped up 2- 3 days by doing so.
Hope this helps.