Your State Pension is likely to be the foundation of your retirement income. But unlike a workplace or personal pension, you do not get a statement through the post each year telling you exactly what you will receive. Instead, the onus is on you to check your National Insurance record, understand any gaps, and decide whether to fill them. The good news is that it is straightforward to do, and a little admin now can make a real difference to your weekly income later.

Why your National Insurance record matters

To get the full new State Pension, you generally need 35 qualifying years of National Insurance contributions or credits. You need at least 10 qualifying years to get anything at all. A qualifying year is a tax year in which you paid enough National Insurance, received National Insurance credits, or paid voluntary contributions. Gaps in your record can reduce your State Pension, sometimes by several pounds a week for each missing year.

It is worth knowing that the rules changed in April 2016. If you have a mixture of years under the old and new systems, your forecast will use transitional arrangements. That can make your record more complicated, but the principle is the same: more qualifying years usually mean a higher pension, up to the maximum.

How to check your State Pension forecast and record

The quickest way is to use the government's online service. You can view your National Insurance record, see any gaps, and get a State Pension forecast. The forecast will tell you how much you might get at State Pension age, and whether you can improve it. You can also request a statement by post if you prefer.

When you look at your record, check for:

• Years where you were working but not paying enough National Insurance, for example because you were low-paid or self-employed with small profits.
• Years when you were claiming benefits, caring for someone, or raising children, which may already have generated credits.
• Any years that show as "not full" but could be filled with voluntary contributions.
• Periods when you were contracted out of the additional State Pension, which may reduce your forecast under the new rules.

Filling gaps: when it pays and when it does not

Voluntary Class 3 National Insurance contributions are the usual way to fill gaps. They usually cost around £17 a week, or just over £900 for a full year. That can sound like a lot, but one extra qualifying year might add around £5 to £6 a week to your State Pension for life. Over a 20-year retirement, that is thousands of pounds.

However, not every gap is worth filling. If you already have 35 qualifying years, paying more will not increase your State Pension. If you are close to State Pension age, it may still be worth it, but check the forecast first. Some gaps from before April 2016 may not be worth filling if you were contracted out. And if you are likely to qualify for Pension Credit or other means-tested benefits, a higher State Pension could reduce those payments. Always get a forecast before parting with money.

Credits and overlooked qualifying years

Many people have more qualifying years than they realise. National Insurance credits can fill gaps when you are not working. You may get credits if you:

• Claim Child Benefit for a child under 12 (and you can still claim credits even if you have opted out of receiving the payments because of the high-income charge).
• Care for a sick or disabled person for at least 20 hours a week.
• Receive certain benefits, such as Jobseeker's Allowance, Employment and Support Allowance, or Maternity Allowance.
• Are a grandparent or other family member caring for a child under 12 while their parent works, through specified adult childcare credits.

It is worth checking these credits have been applied. Mistakes happen, and missing credits can often be corrected years later.

Deferring your State Pension

You do not have to claim your State Pension when you reach State Pension age. If you defer, you can increase your eventual weekly payment. Under the new State Pension, deferring increases your pension by 1% for every 9 weeks you delay. That works out at about 5.8% for a full year. If you defer for at least 12 months, you may be able to take a lump sum instead, though this is taxable.

Deferring can be a good move if you are still working, have other income, or expect to live a long life. But it is not right for everyone. If you need the money now, or your health is poor, claiming as soon as you can is usually sensible. Also consider tax: extra State Pension is taxable, and a lump sum could push you into a higher band.

Putting it into practice

Start by checking your State Pension forecast and National Insurance record online. Note any gaps and the cost to fill them. Then ask yourself three questions: Will filling this gap actually increase my pension? Can I afford the voluntary contribution? And is deferring likely to be worthwhile for me? If you are unsure, the government's free pension guidance service offers impartial help for people over 50. A little time spent now can mean a more comfortable retirement later.