The first Monday in February may be best known as National Sickie Day, but new figures suggest it is no longer the biggest flashpoint for sickness absence in the UK, with other winter Mondays proving far worse for employers.
Analysis of workplace absence records shows sickness levels peaked on Monday 6 January last year, when absences rose sharply above the daily average. By contrast, National Sickie Day finished only fourth in the annual rankings, continuing a decade-long trend in which it has failed to top the table.
The data was compiled by people management firm BrightHR, which analysed 2025 absence records from more than 1.2 million employees working across 120,000 UK businesses. It found that the ten worst days for sickness absence during the year were all Mondays, underlining the role of winter pressures and the start-of-week effect on attendance.
Winter Mondays drive absence spikes
According to the analysis, sickness absences rose by 182 percent on Monday 6 January compared with the average daily rate for the year, making it the single worst day for absence in 2025. National Sickie Day, which fell on 3 February, saw a smaller but still significant spike of 146 percent.
The concentration of absence on Mondays reflects a familiar pattern for employers. Cold and flu viruses circulate more widely during winter months, while the return to work after weekends and holidays can coincide with fatigue, disrupted routines and pressure on mental health.
The figures also showed that certain cities experienced particularly sharp spikes on National Sickie Day. Blackpool recorded the highest increase at 265 percent, followed by Norwich at 236 percent, Cambridge at 223 percent, Aberdeen at 216 percent and Leicester at 204 percent.
While the data does not suggest deliberate misuse of sick leave, the scale of the increases points to regional patterns that employers may need to understand more closely, particularly in sectors with limited staffing cover.
Younger workers most likely to take sick leave
The analysis also found generational differences in sickness absence. Generation Z employees were the most likely age group to take time off sick, with an average of four in five having taken sickness absence at some point during the year.
Younger workers are more likely to work in customer-facing or lower-paid roles where exposure to illness is higher and the option to work from home may be limited. They may also be more open about taking time off for mental health reasons, a factor that has become more visible since the pandemic.
By contrast, older employees were less likely to record sickness absence, which may reflect differences in job security, flexibility or attitudes towards attendance.
Cost pressures intensify under new sick pay rules
The findings come at a sensitive time for employers, with changes to sick pay rules set to increase the direct cost of absence. From April this year, statutory sick pay applies from the first day of absence, following changes introduced under the Employment Rights Act 2025.
BrightHR estimated that on the single worst day for sickness absence next year, the introduction of day-one sick pay could cost UK employers at least £5.13 million. The calculation assumes an additional 200,000 workers taking sick leave on that day alone.
Over the course of a year, the firm estimated the wider cost of the Employment Rights Act to businesses at around £1 billion, once higher sick pay liabilities and related changes are factored in.
Using absence data to support wellbeing
Commenting on the findings, Alan Price, chief executive of BrightHR, said National Sickie Day had lost its significance, but winter Mondays remained a major challenge for employers. “Although National Sickie Day itself has now officially popped its clogs, Mondays in winter are still officially the worst for absences, whether due to cold and flu viruses, seasonal pressures on mental health or employees getting creative with reasons why they need a day off,” he said.
Price said tracking absence patterns could help employers support staff more effectively and reduce disruption. “We’re not necessarily suggesting that people called Jack in Blackpool are swinging the lead, however tracking absence patterns does help bosses keep an eye on staff welfare.”
He added that understanding trends could help employers intervene earlier. “Approaching wellbeing from an employee perspective means emphasising the importance of mental health to encourage a culture of openness and support. This way, employers can increase attendance statistics, productivity, and staff retention, rather than scratching their heads wondering why half the workplace is missing again on Monday.”
Warning signs for employers
Price said the scale of the spikes in some cities should prompt closer scrutiny. “Alarm bells should be ringing in the cities where sickies spiked, a more than 200 percent increase is no coincidence. What are the signs that employers are missing?”
He argued that better use of absence data could help organisations identify risks before they escalate. “This is where absence management software comes into its own, identifying trends and patterns before they become a significant risk to business productivity.”
He also pointed to the financial impact of sickness absence under the new rules.
“It’s also key to note the financial impact that sickness absence can have on businesses. Under the Employment Rights Act 2025, Statutory Sick Pay will apply from day one of absence. Our calculations estimate that an additional 200,000 workers will be off on the sickest day next year. That’s a minimum cost of £5.13 million to UK employers, for just one day.”
Planning for 2026
Price said National Sickie Day should be seen as part of a broader picture rather than a standalone issue. “National Sickie Day is a drop in the ocean of extra considerations for employers. In total, the Employment Rights Act 2025 is expected to cost businesses around £1 billion per year. Business leaders will need to look at cost savings in all parts of their business.”
He said employers that understood absence trends would be better placed to plan ahead. “Whether employers have already weathered the storm of sickness or are still battling through winter absences, understanding trends in absence data can help them with workforce planning into 2026.”
The data reinforces the importance of combining compliance with a preventative approach. Clear sickness policies, open conversations about mental health and realistic staffing plans may all play a role in managing absence more effectively as winter pressures and legislative changes converge.
