Client being chased by Iqor debt collection on behalf of HMRC

 The money they are asking for apparently relates to underpaid VAT in 2007. There was some confusion back then as she had paid the VAT amount to the PAYE office in error and there had been letters from HMRC at the time.  Anyway we had confirmation then that the amount had been transferred to the VAT account and the matter was settled as far as we were aware.

I am very concerned now that this exact amount has come again and being chased by a very persistent debt collection agency. Do HMRC use such agencies to collect debt?  If not how does this company have the information on my client.

Has anyone else come across this?

Debbie