These rules apply to men born before 6 April 1951 and women born before 6 April 1953. There are different rules for younger people.
You need 30 years of National Insurance contributions to get a full state pension. If you have fewer than 30 years National Insurance contributions you will get a reduced pension. So if you have 20 years you will get 2/3rds of a full pension.
It is now no longer possible to pay extra contributions to fill any gaps.
That is because you can only fill a gap which is up to six years old. So now, in 2022/23, you could only fill gaps back to and including the tax year 2016/17. But by then you would have reached state pension age and cannot pay earlier contributions.
4 May 2022