Update! - The deadline to make any payments to close NIC gaps has now been extended from July 31st 2023 to April 5th 2025, so you have over 20 months extra to potential benefit from thousands on your pension.
Visit the Government's state pension forecast calculator at gov.uk/check-state-pension. You will instantly see an official record of your NIC payments until now (gov.uk/check your national insurance record), as well as what your predicted state pension payments will be based on this and you working up to state pension age.
If the predicted amount of state pension for you is less than £185.15 this means you have periods in your employment history where not enough NICs were paid.
The reason this is important to know is that a new state pension system came into effect on 6 April 2016, meaning that most people aged 70 or under should pay attention to upcoming changes.
The maximum amount you can currently receive as state pension is £185.15 per week, but this depends on how many "qualifying" national insurance (NI) years you have. You usually need to have 35 full qualifying years, although this can differ based on your age and NI record.
To make it easier for people to get the maximum amount of state pension, there are "transitional arrangements" in place. This means that you can pay to close any gaps in your NI record from as far back as 2006. This offer expires on 31 July 2023 (now extended to 5 April 2025), after which you can only fill gaps from the last 6 tax years.
For some people, paying to close gaps in their NIC record could mean they receive thousands more in state pension.
You might not even have to pay to close the gaps if you can claim NI credits. These are years where you may have underpaid NICs due to being in circumstances like statutory sick pay, job seeker's, caregiver, jury duty, since overturned jail time, maternity/paternity, adoption, government training courses, armed forces member/spouse of member.
NI credits can be claimed directly from the government at gov.uk/national-insurance-credits/eligibility.
Those near state pension age should consider topping up if their pension will be less than the full amount, and they can't fill the gaps in any other way. People over 45 and some way off state pension age need to need to figure out if they will be able to reach the 35 years of qualifying NICs before retirement age - otherwise should top up. The younger you are, the more time you have to earn enough qualifying years before you reach state pension age - but, it may be cheap to top up in case of future periods of NIC underpayment.
It all depends on how many years you feel you will claim the state pension versus how much it costs to top up. Each top up year costs about £850.