Student Loan Underpayment on Self Assesment

Hi,

I'm hoping I can seek some advice on this.

I have always been paid on PAYE however I did a self assessment for TY 13/14 to claim Business Mileage tax relief, essentially I did it once didn't realise I had to do it subsequently (my fault) and in combination with HMRC having an old address I found out recently that I had to submit tax returns for 14/15, 15/16 & 16/17.

In doing so my tax has pretty much balanced out as I was put on a higher code when I first did it however what has become apparent is that my employer started taking Student Loan payments too late (08/15 instead of 04/14) (I should have realised also so I'm not dodging responsibility here) this then shows an underpayment across 2 tax years of around £4,200 in income contingent Student Loan which HMRC are requesting to be settled now.

Since then through my further payments I have paid off about 30% of the loan and student loans company have told me they wouldn't ordinarily ask for that amount up-front as its being paid off anyway I also read that under normal PAYE payments just continue to be taken until paid off rather than requesting anything up-front.

So I now have around 7 days to either come up with the funds and pay off HMRC or go on a very high interest payment plan with HMRC over the next 12 months.

I'm keen to understand if anyone knows of another option here or whether the above is my only option.

Thanks in advance for your help.