Tax evasion is illegal activity, where registered individuals or businesses deliberately omit, conceal or misrepresent information so they can reduce their tax liabilities.
Tax avoidance is exploiting the tax rules to gain a tax advantage that Parliament never intended. It often involves contrived, artificial transactions that serve little or no commercial purpose other than to produce a tax advantage. It involves operating within the letter, but not the spirit of the law.
For further information on this I refer the Noble Lord to Table 1.6 in the ‘Measuring Tax Gaps 2014’ publication available on gov.uk.