The likelihood of HMRC swooping to investigate your business’s tax affairs seems to be a particularly difficult risk to quantify. In 2017, the Government published a report called ‘Understanding evasion by small and mid-sized businesses’.
The authors interviewed 45 people known to have engaged in deliberate tax evasion in an attempt to get to the bottom of what made them risk it. It found that tax evaders cited a range of reasons for withholding tax. Some judged the risk of detection to be low, and assumed evasion would be hard to prove even when suspected, or thought that any fine they did incur would be outweighed by the financial benefits of bending the rules. Others were emboldened by a belief that, to paraphrase, “everybody does it, and nobody cares.”
However, with HMRC ramping up its investigations to boost tax revenue, it's not a risk worth taking.