If the details on an IN are incorrect, e.g. compliance date, does it make the notice invalid?

Can you elaborate so we know what excatly you mean by the compliance date is wrong. If it is not the date you agreed then that doesn't make the Notice invalid. But you might want to phone up the inspector and have a chat about it. But you cannot just decide it's invalid. Phone. Check.

Then in effect you've breacxhed your IN!! But I assume the inspector signed it off at a date later than January 2011 and so the mistake would be obvious to anyone. I'd ring the inspector concerned and point out their mistake.

Murray - The expiry (i.e. comply by) date for the Improvement Notice (IN) could just over 3 weeks from the date it was signed by the inspector - the period available for formally appealing against an IN if a recipient thinks there are valid grounds why it should not have been served and/or it cannot be complied with. However, in this case, the inspector probably forgot to write/type the actual date number before the month name January. Inspectors are human and thus just as prone to errors, including typing omissions, as the rest of us. As others have already pointed out in their responses, contact the inspector to ask about the date. If the date number was simply omitted from the original version of the IN , he/she will probably send a corrected version. Furthermore, if you and your organisation agrees that the IN is otherwise valid and intends to comply with its requirements by sometime in January, what's the problem? On a general note for all forum users, if any recipient of an improvement or prohibition notice from HSE is unsure about any aspect of it, it's always sensible to promptly contact the inspector who served it. Also, if a recipient of an IN intends to comply with it by the expiry date and then experiences a genuine problem which is likely to delay compliance, do tell the inspector BEFORE the expiry date and ask for an extension of the IN. If the inspector thinks a recipient has genuine grounds for this, he/she will send a formal document which includes the IN reference details and a later date for compliance with it. It's best for an IN recipient to request an extension as soon as the need for it becomes known and also to indicate what compliance measures have already been taken and/or are planned. If an extension request is sought just before the expiry date, some good convincing information will need to be given to persuade the inspector that the recipient has not simply ignored the IN and is therefore having a last minute panic about the prospect of being found in breach of it.