HM Rev outstanding TAX claim

Hi.

We are struggling to get a grip on all the the new OPPT developments. I think it is just the huge amount of new info that needs to be digested.
In the meantime - my wife had to give up her business and she is facing the HM Rev. She worked incredibly hard in her little business until a medical condition out of her control placed her in position in which she could not hold her 'thumb' on things and she started loosing money with.., well, good meaning staff not doing it right. Working while receiving treatment also made things worse for her and her financial position - thus she had to get out.
A greedy landlord skillfully prevented her 'legally' from selling her lease and we had to walk out with nothing. He had sold her business in the meantime...
Back to our problem - looking at the strawman and everything concerned. Can anyone point us in the right direction of how she should handle the HM Rev claim of outstanding TAX?
How does one deal with the threat of the Sheriff coming to collect? Can OPPT action even prevent this from happening?
Much appreciated!

No one.., no ideas.., no suggestions? Can the OPPT notices not be applied somehow?

I have a similar situation. Built up a company over many years, ended up backing it with my home which i then had to sell to keep it all going. But it all did not make it in the end, lost the lot and I have nothing to cover any outstanding claims.

So I am considering using the courtesy notice. As far as I can see this is all that should be required along with following up on the invoicing. But I would like to be certain that it applies to the uk system as it seems to be the heart of the beast in many ways.