Yes, held the EAT in Sterling v United Learning Trust.
In this cautionary tale the employee submitted her ET1 'missing some digits from the EC number, the tribunal inferred' four days before the expiry of the limitation period. It was returned to her by the tribunal office two days later, with an accompanying letter. The address cited by the office was neither that of her representative nor her home. It ultimately arrived at a neighbour's house and the employee re-submitted straightaway, albeit out of time.
On appeal the employee argued that the employment tribunal was not entitled to make such an inference but the EAT (Langstaff J) disagreed. Rule 10(1)(c)(i) obliges the employment tribunal to reject a claim if the EC number is missing, although a party may apply for a reconsideration of such a rejection. No such application was made by the employee's representative, and even though he was not legally qualified the EAT said the employment tribunal was entitled to conclude that no such application was forthcoming.
The representative also failed to argue that it was not reasonably practicable for the employee to have lodged the claim in time. The EAT dismissed the employee's challenge to this aspect of the judgment, making it clear that the burden was on her to prove that it was not reasonably practicable and that even if the point had not been argued originally there was a duty on the employee to ensure that the EC number was cited correctly.