Warnings are appearing in various forms of the media to check your Tax Code . I have been a â victim â of the new Tax Code Software being used by HMRC . In May of last year everything was normal and out of the blue I received a new Tax Code and chaos developed . In a period of six months since then I have telephoned and written to HMRC and have had a further six Tax Codes â¦ I am now where I was back in May . The annoying thing is that my Pension suppliers were acting on new Tax Codes as they received them and deducting what they incorrectly believed to be unpaid Tax . I have been further advised that any errors in my Tax paid this year will not be corrected until the Tax year 2011/2012 . I do not blame the software but the way it has been rolled out apparently without adequate parallel testing â¦ why does the Public Sector always seem to have problems with such work ? I have been involved in the implementation of complete Business Solution IT Projects in the private sector where failure was not an option on the go live date .