It's not a situation to relish, having the taxman - HM Revenue & Customs (HMRC) - investigate your financial and fiscal circumstances.
But there are things you can do to make the process quicker and hopefully easier.
Although everyone's situation can vary drastically, here's This is Money's top 10 tips on what to do (and indeed, what not to) if you are being investigated by HMRC.
1. Don't panic!
Just because you are being investigated, it does not mean it will necessarily be the end of the world. Even if you have been careless, remember very few cases actually end in a custodial sentence.
2. Get advice
If you are being investigated by HMRC, it is highly recommended that you seek out independent financial advice from a reputable accountant or adviser. It's likely to be cheaper, not to mention easier, in the long run.#
3. Keep it quiet
Don't discuss your tax affairs with anyone but a tight circle of tax advisers. Your best friend's advice and thoughts on the matter may not be what you need and they are more than likely going to get it wrong.
And when you settle with the taxman, don't go bragging about it – boasting about what a great deal you got can be a very bad idea. Fiona Fernie, at accountancy firm BDO Stoy Hayward, points out: 'You never know who is listening, things can, and do, get back to the taxman, and the case against you could even be re-opened.'
4. Tell the truth
Don't, under any circumstances, lie to HMRC. In the long run it'll do you no favours.
5. Don't underestimate the taxman
Don't assume HMRC is ignorant of anything. It will amaze you the level of resources that the taxman has at his disposal.
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6. Be prepared
Be well prepared for any meetings, you need to be aware of what you might/will be asked, so have enough prepared to be able to give adequate answers.
7. Pay up ASAP
Make significant payments on account. In other words, if you are fairly confident on what settlement you need to make - then pay up as soon as you can. Not only does it show co-operation but it could also potentially save you a small fortune in interest, which can accrue on a daily basis. But don't massively overpay either, as it could be a drawn-out process getting your cash back.
8. Don't destroy evidence
Don't try to destroy evidence. If you don't have the paperwork, HMRC may assume you are trying to hide significantly more than you actually are. As a result it may treat your case even more seriously and the process could be prolongued. HMRC can invetsigate back as far as 20 years if it thinks your case warrants such examination.
9. Tell the whole story
Do not suffer from selective amnesia – don't tell half the story and wait for HMRC to catch up. In very serious cases, false or deliberately misleading statements can result in prosecution.
10. Don't reoffend
Once you've settled, save yourself time and money and don't re-offend again. HMRC could, and most likely, will be harsher on a re-offender.
Updated, July 2009, Philip Scott, This is Money