I previously worked for an employer which did not have a sickness absence policy, every case in which an employee was absent was dealt with under its disciplinary policy. This was a strange and counterproductive approach to take as it conveyed a clear message to staff that to be ill to the extent that one’s ability to work was impacted was to be culpable for wrongdoing. In practice most managers adopted a sensible approach but the policy drafted by the organisation’s HR officers (a large quasi-public health body that really should have known better) sent out a strong message to those who were ill that they were on shaky ground if they looked after their own health – and often those of colleagues – and that doing so would please them at risk of disciplinary sanction.
For this reason many employers, especially in unionised settings, do not treat sickness absences in and of themselves as disciplinary matters. In an unfair dismissal context an employer could dismiss an employee who had had an unacceptable level of sickness absence under two of the five potentially fair reasons for dismissal: conduct or capability. It is not hard to see that an employer relying on conduct as a reason for dismissal will quite quickly run into problems when seeking to justify a dismissal on this ground where the absences are entirely genuine, even if this is a significant burden on the employer. By contrast, there the decision is capability it is a decision much easier to justify.
The point is that a sickness absence approach – which is one that focuses on capability – is one much easier to justify, this approach does not prevent a system of warnings but the focus is very different.
Although it was not a sickness case many tribunals when considering the conduct/capability cite the decision of Sutton and Gates (Luton) Ltd v Boxall  IRLR 486. Boxall concerned an electrician who was evidently not a very good electrician, although his work was normally rated ‘adequate’. When taking a period of holiday the claimant was dismissed. The employer had received requests from clients not to send the claimant on jobs because of the relative poor quality of the work he did. In Boxall the following guidance was given on identifying whether a dismissal should be considered to be because of conduct or capability:
We have had occasion to indicate more than once that it may not necessarily be that there is a wide range in the field of incapability, but that incapability ought to be treated much more narrowly and strictly than has been done in the past; and cases where a person has not come up to standard through his own carelessness, negligence or may be idleness are much more appropriately dealt with as cases of conduct or misconduct rather than of capability. It means of course that Industrial Tribunals, as argued in this instant case, may well be in danger of misdirecting themselves unless they clearly distinguish in their own minds how far it is a question of sheer incapability due to an inherent incapacity to function, compared with a failure to exercise to the full such talent as is possessed.
Applying this approach to the question of sickness absence it is clear that in the vast majority of cases where there is no evidence of anything other genuine absence then a reasonable employer should treat excess absences as a capability rather than conduct matter.
However, where an employer has reason to think that an absence is attributable, to quote from Boxall, to an employee’s “carelessness, negligence or … idleness” then a disciplinary approach may be possible, if the employer has a reasonable belief (and has conducted a reasonable investigation) that the employee did engage in culpable conduct realted to sickness absence. To give an example, in Ajaj v Metroline West Limited UKEAT/0295/15/RN an employee embellished the extent of his sickness making it more of an impediment to his ability to work that it really was. The EAT found that where a employee ‘pulls a sickie’ this will often amount to gross misconduct:
Mr Ohringer faintly suggested that absence from work based on an assertion that one is unfit to work might give an employer grounds to dismiss, but would not necessarily amount to gross misconduct. I disagree: an employee “pulls a sickie” is representing that he is unable to attend work by reason of sickness. If that person is not sick, that seems to me to amount to dishonesty and to a fundamental breach of the trust and confidence that is at the heart of the employer/employee relationship.
That does not mean a dismissal for ‘pulling a sickie’ will always be reasonable but it does indicate that it is in a situation where there is culpable conduct that a sickness absence will be most appropriately considered to be one of conduct rather than capability.