P45 for LEL employee

A sole trader employees a worker paid under the LEL. HMRC says that ST doesn't have to register as employer, PAYE or submit FPS (which would require a PAYE ref). Now employee has left and had requested a P45. How can I produce that given the above. I'm told to use basic PAYE tool but that needs PAYE reference. Any help welcome.

Hi William Croomec,
If you have established that you did not need to run a payroll then you wouldnt have the P45, can you please contact us on 0300 200 3200 to discuss this further.
Thank you.