Under s.13 of the Employment Rights Act 1996 an employer must not make a deduction from wages from a worker unless authorised by a statutory provision or by the worker's contract, or unless the worker has previously signified in writing his agreement or consent to the deduction.

Under S.23 of the ERA a worker may complain to an employment tribunal to recover the deduction from the wages concerned. However, it is a strict rule that such sums from which a deduction was made have been "properly payable" to the worker in the first place.

In Agarwal v Cardiff University the EAT has confirmed that an employment tribunal does not have jurisdiction to hear and determine a claim under section 13 of the ERA if it requires a decision on the construction of the employment contract. In this regard the EAT followed the decision of the Court of Appeal in Southern Cross Healthcare Co Ltd v Perkins [2011] ICR 285. In that case the Court of Appeal held that an employment tribunal has no jurisdiction to construe a statement of written particulars in a claim for non compliance by an employee to supply particulars under s.11 of the ERA 1996. That applies equally where it is necessary to construe a contract in order to determine a claim under s.13 of the ERA not to suffer an unauthorised deduction from wages.

In this case the claimant was employed under what was described as a "clinical academic contract", performing both lecturing duties for Cardiff University and clinical duties for Cardiff and Vale University Local Health Board. Following sickness absence the claimant returned to her lecturing duties, but not her clinical duties (as there were interpersonal issues to be resolved), and therefore was paid half her salary as a result. She brought a claim under section 13 of the ERA 1996 claiming that she had suffered unauthorised deductions from her wages in respect of the clinical sessions. An employment tribunal dismissed her claim on the basis that it did not have jurisdiction to hear it, as it was not possible to determine the claim without having to engage in the construction of the employment arrangements with Cardiff University and the Health Board, the terms of which, and the relationship between which, were in dispute.

The EAT agreed. If, therefore, the terms of the worker's entitlement are in dispute the employee must pursue an alternative remedy, by way of a contractual claim before an employment tribunal under the Employment Tribunals Extension of Jurisdiction (England and Wales) Order 1994 (if the employment has ended) or by a contract claim in the civil courts.