When was your last year of NIC payment?
In any event, if you’ve been approved to pay any past years ….pay them all immediately in case the rules or cost changes. You are unlikely to be offered a better financial return ever again! The one proviso is that you have to live for a certain period of time after pension payments begin, to get your return on investment.
Going forward and after the current catch up deadline expires in 2025, you will only be able to go back six years. That’s assuming the current rules continue as they are.
You have a choice whether to pay your NIC annually or to allow up to 6 years to accrue and then pay them together. In my case I have paid 16 years as a lump sum payment in 2022 and later one annual payment for tax year 2022/2023. I have 4 years left to go to get the maximum and intend to pay NICS annually. For me it’s a good habit to ensure I don’t overlook it or lose out to rule changes.
In addition, if I continue to make annual payments I expect to get an annual reminder from HMRC. If I allow a tax year to go by without a payment I understand that the reminders stop after a few years of non payments.