Online access denied

I have been forwarded a notice from a client that says he has underpaid his PAYE and National Insurance contributions for the 2011/12 tax year; he has asked that I look into this.

As in previous years I started by calling the HMRC accounts office and was greeted by an automated message advising it no longer provides details of the monthly or quarterly payments but that this information is available using the online service.

Since I am aware HMRC are looking for agents to have more control over their client records at the department I thought this was a move in the right direction. That thought soon evaporated when I could not find the relevant link on my clients records.

My next thought was that I was looking in the wrong place. I called the online help service which advised me that HMRC online access to...