Not sure if its relevant or if it covers commission but...
The Wages Act 1986, seeks in part to protect employee's wages, by prohibiting deductions, save for tax, national insurance, and attachment of earnings orders. For money to be deducted in accordance with the Wages Act 1986, the employee must have given their express written agreement, or provision should be made for the practice, detailing precise circumstances, in the contract of employment. The latter would be the subject of scrutiny by the Tribunal, and hence it is vitally important to ensure that such contractual documentation is adequately worded. In practice, this means an employee may owe the company money, in respect of damage to company property for example, but the employer is NOT legally entitled to deduct money from wages.