Hi. During an IVA you always owe the original debt, plus fees and possible statutory interest.
Using quick, "on the back of a cigarette packet" calculations, which are very rough and assume the usual fee structure (which is far from guaranteed to be the case) :
To achieve 100% payback on a £9000 debt would require around £15450 to be paid over on a 5 year term. Taking off a years statutory interest, would mean a payment of £14730 to close at the end of year 4.
In her 4 years your mum has paid in £4840, plus the PPI.
Of the £12,000 PPI recovered, around 30% would be lost in recovery company fees, leaving £8400 for the IVA, of which 15% will go in IPs fees, so, in reality, only £7140 will reach creditors.
So, the IVA has had around £11,980 paid in, which is still short of the amount needed to close early.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014