Basic state pension

Salaam Alaikum,

My husband and I have been out of the UK for many years and therefore have contributed very little to a state pension for retirement. I understand from hmrc that we are able to pay backdated voluntary contributions to make up for some years of the shortfall.

Please advise if this is impermissible as I am assuming that some of the funds are not invested in a shariah compliant manner. Is there a way of purifying the income by means of some type of calculation?

Unfortunately many of the shariah compliant funds available now were not available to us in the past and so we avoided most types of investment. I do have a concern that we will miss out on a basic pension afforded to most people living in the UK.

Jazakallahu khairun

Wasalam

May Allah bless you.
Yes, is it permissible.
State pension is usually paid through NI contributions. During the contribution period, the money is not invested on your behalf. Instead, it is usually used to pay other state benefits to other people.
When you will retire, your state pension will be paid from future NI contributions of other members of society.

And Allah knows best!