A redundancy payment is based on “a week’s pay” (subject to the statutory cap) and takes into account the employee’s age and the number of years of employment. Years of employment count equally for this purpose regardless of whether the employee worked full time or part time.
However, the issue is how the “week’s pay” is calculated. Where the employee is required under the contract of employment to work during normal working hours on days of the week or at times of the day that differ from week to week or over a longer period (so that pay varies from week to week), the amount of a week’s pay is based on the average pay and the average number of hours worked in the last 12 weeks before the calculation date.
I would say that, as there have been two periods of maternity leave and a period of part-time working, the redundancy payment may be calculated on the above averages.
When calculating redundancy when someone is on maternity leave statutory redundancy pay should be calculated using the normal week’s pay or average week’s pay received before the maternity leave period started. It should not be based on SMP or contractual maternity pay.
This is somewhat complicated and depends on whether you have normal working hours or not. It will also depend on what your contract states, and what hours/ days you return to after your maternity leave and how long for. Additionally, it will depend on whether your company offers statutory or enhanced maternity leave.