I have only just discovered this highly beneficial piece of legislation when looking at my pension situation.
I'm Grandma in my early sixties, a few years off state retirement age, already receive a private pension. For various reasons I do not, and won't have, 35 years of NI to enable me to get the full state pension.
However, there's a way of boosting your eligible years if you have done childcare for your grandchild( under 12 years old) in any periods since 2011. If the child's parent claims Child Benefit and pays NI through working they in effect have double NI credits. For any periods you have cared for your grandchild, with mutual agreement, you can claim to have the "spare" NI credits from their child benefit transferred to you, thereby increasing your eligible years for state pension. There is no minimum amount of caring, you just have to state that you did it.
Claims can be backdated to 2011. My claim will mean that I'll get 9 extra years added to my eligible pension years, which is going to give me hundreds of pounds more in state pension every month than I would otherwise receive.
All you need to do is fill in the relevant form on gov.uk and you and the child benefit recipient both sign.
I wasn't aware of this until last week so there may be other grandparents in a similar situation who could benefit.