Here's a link to a sound file of the half hour radio episode first aired fifty years ago on 4 November 1956.
Tony Hancock receives a tax demand for £14 12s 3d re ten years' back tax. He refuses to pay as that represents 50% of his income over the period! (Even fifty years ago this would have been a tiny amount!) so he goes to see the Inspector - played by Kenneth Williams.
The inspector tells Hancock that most people ignore his letters. Once they've been ignored twice he ignores the taxpayers! He also recommends that Hancock should go to see a Chartered Accountant "you'll probably get away with it then!". Hancock takes his advice but the accountant turns out to be a crooked Sid James and mayhem ensues.
I am indebted to Chris Chadburn for telling me about this.