Inland Revenue/Customs joined forces some time ago and basically have been in disary since, the loss 0f 20,000 jobs did not help along with closing local centres and trying to centralise only added to the confusion.
There has been a conserted effort to 'go after' small business's as trying to pin down the larger organisation costs them more in time and money and invariably they lose, this is part of the cost cutting measures.
How do I know this? my book keeper was one of those laid off, vastly experienced time served replaced by online system or cheaper youngsters.He obviously keeps in contact with former collegues who inform him they are under huge stress to try and clear backlogs, mistakes will be made.
Don't take a chance, if they have not contacted you go after them or pay on line. Regardless if you think its their error
you will have to pay for it.