Your National Insurance number, and why it matters more than you thinkMoney · 4 minute readIt turns up in the post when you are about 16 and looks like junk mail. It is not junk mail. Here is what it is, where to keep it, and the three times you will need it.A letter arrives with a number on it, you read half of it, and it goes in a drawer. That number is your National Insurance number, and it is the thread that joins you to every job, every tax payment and every pension you will ever have in the UK.What it actually isIt is a personal reference number that is yours for life. It is not a card, it is not an ID document, and it does not expire. You cannot apply for one before you are 16 unless you need it earlier, and you never need to renew it.In practice it is how HMRC knows that the tax paid by 'J Smith at the chip shop' and the tax paid by 'J Smith at the warehouse' are the same person — and therefore that you have not paid too much.The three times you will use it

Starting any job, including a weekend or holiday job. Your employer needs it to pay you correctly.

Setting up as self-employed, or doing paid work on the side that you need to declare.

Anything to do with tax, benefits, student finance or your state pension.

Where to keep itPhotograph it and keep the photo somewhere you will still have in five years. Write the number down in a place you control. Then put the original letter somewhere safe.Never give your National Insurance number to someone who contacted you first. Banks, HMRC and employers do not ring you out of the blue asking for it. If someone does, put the phone down.If you lose itYou can find it on a payslip, on a P60 from an old job, or in your HMRC online account. If you genuinely cannot find it anywhere, you can ask HMRC to post it to you — it does not come back instantly, so start before you need it rather than the week you start a new job.Nobody sits a 16-year-old down and explains that this boring letter is one of the most useful pieces of paperwork they will ever own. So here it is, explained.More free articles about money, work and business are at The Next Generation Blog.

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