Each insurer informs their clients of pricing in different ways, some yearly, some monthly and some pro-rata yearly. Ultimately insurance is based on a daily amount which is then multipled by 30.4166 to get monthly (365/12) or by 365 to get yearly*.
* note this changes to 366 on a leap year
Happl payroll dates run based on live dates and do not forecast the future so if you payroll cut off is the 20th and it is a monthly payroll then each payroll report would look at usage within the 21st to the 20th the following month (inclusive).
When calculating insurance this can differ each month so Happl takes an average approach to get the number correct. We do this be having a start middle and end month calculation.
The start month is the exact number of days x the day rate.
The middle is day rate x 30.41666
The end month is total days insured x day rate minus what has been charged so far (so the start and however many middle months)
For example:
20th payroll cut off date
I join the policy on the 15th October 2025
I leave the policy on the 1st March 2026
£600 yearly premium
Daily rate is 600/365 which is £1.6438356164
I join the policy on the 15th of the month, so I have it for 6 days (15,16,17,18,19,20) so my first month amount is £9.86 (rounded)
Then my middle months are charged at £49.99 (rounded)
And then if I left the policy after 6 months on the 2nd of the month I would need to pay the remaining amount
So if I had been on the policy for 139 days in total the amount I should have paid is £228.49
So then the 6 months:
Month 1 - 15 October to 20 October - £9.86
Month 2 - 21 October to 20 November - £49.99
Month 3 - 21 November to 20 December - £49.99
Month 4 - 21 December to 20 January - £49.99
Month 5 - 21 January to 20 Febuary - £49.99
Month 6 - 21 February to 2nd March, so I pay:
Total paid is £209.82
Amount to pay £228.49
Final amount to pay = £228.49 - £209.82 = £18.67 to pay in the final month