“Citibank has won an employment tribunal after sacking a worker for claiming expenses for sandwiches and coffee for his partner.” This short sentence taken from a recent BBC article summarises the unsuccessful claim of unfair dismissal by a former senior analyst of Citibank.

On first reading, the fact that the employee was dismissed for gross misconduct may seem incredibly harsh under the circumstances, particularly when their expense claim was within the daily limit set by the employer. Hardly deserving, some might think, of being treated as gross misconduct and dismissed without notice. The key issue however was that the employee had initially lied about the fact that their expense claim included a coffee and sandwich for their partner, which wasn’t permitted under the expenses policy.

Whilst the cost was minimal, it was this initial dishonesty that led to the employee’s dismissal. The fact that the dismissal was found to be fair by the employment tribunal underlines the special quality which must be preserved for an employment relationship to continue: mutual trust and confidence.

The term is most often seen when an employee resigns and claims that the poor conduct of their employer over an extended period amounts to a dismissal (constructive dismissal). In these such circumstances, the employer may not have breached any key term of the employee’s contract, but breaching this implied duty will still be viewed serious enough to justify the employee treating the contract as fundamentally broken by the employer.

However, the Citibank case shows that the duty is a mutual one. Whilst the value of a coffee and sandwich may be incidental, it’s a question of whether the employer can truly trust the employee to carry out the functions of their role. The expectation of honesty from the employer was particularly pertinent in the Citibank case, as the judge highlighted that the employee was employed in a “position of trust” in a global financial institution. Nevertheless, all employees are engaged in a position of trust to some extent and any dishonest act will have a significant, if not fatal, impact on the employer’s ability to trust them in the future.

An employer can’t simply assert “I don’t trust you” and rely on the implied duty to terminate employment. They must still be able to demonstrate that there’s been dishonesty (or at least that they reasonably believe that to be the case) and have carried out a reasonable investigation.

Thinking about the underlying duty of mutual trust and confidence can be a helpful tool for employers in deciding what an appropriate sanction would be in a disciplinary process. A dismissal will only be unfair if it falls outside of the “band of reasonable responses” which an employer might consider. If an employer can credibly say that they don’t trust an employee anymore because of their behaviour, then dismissal will be justifiable.

Euan Bruce is a legal director in DLA Piper’s Employment practice in Scotland