Sell in Amazon Japan if based in the UK

Hi, Me again…
Ever busy!
I’ve recently set up an Amazon Japan account with new selle
r details and it’s all gone through OK. I am however having trouble getting my stock cleared through customs - or so it would appear from UPS.
I have been asked to supply an invoice - " I cannot be the importer if I am the shipper…".Ca anyone give me some help as I’m a little stuck and would rather not abandon this and return the stock to me here.
thanks
Aidan