N & H

I'm hoping someone can offer some advice. We completed all of our 143 paperwork in the UK and completed the pre-payment online via our Immi account. We included our payment reference number on our application. We then posted our completed documents to our son (sponsor) who lives in Perth WA, he is going to complete his sponsor documents and post to the immigration office in WA once complete. I posted our documents via Royal Mail international signed for service 18 days ago and they still haven't arrived with my son. Does anyone know what happens if your application is lodged over 30 days after you have pre-paid online? Thanks in advance