Are you sitting on hidden treasure worth £10,000s? This isn’t about a forgotten lottery ticket stuck to your fridge or a sepia map in the attic to Long John Silver’s hoard. It’s a more mundane, but far larger – there's £15 billion sitting in lost bank accounts, savings, pensions and investments.

It may be yours or a deceased relative's, and is relatively easy to claim. So check my top ten need-to-knows…

1. Trace old Premium Bonds

The name's Bond, forgotten Bond. There's £44 million in Premium Bond prizes sitting unclaimed, owed to 900,000 people. To get these, follow a simple two-step process.

First track down what bonds you own. If you don’t have them, trace for free at www.mylostaccount.org.uk. Then nip onto www.nsandi.com and use its prize checker to see if you're missing out.

2. Bank accounts reunited

There's £500 million languishing in forgotten bank accounts and savings. While the accounts go dormant, you’re still entitled to the cash if you claim. If you think some could be yours, use free one-stop shop www.mylostaccount.org.uk to get it back.

3. "I found a £21,000 pension"

Pensions are almost always big money. Yet with many frequently moving jobs and pension confusion, it's not surprising schemes get forgotten. To get it back, use the Pensions Tracing Service at www.gov.uk/find-lost-pension.

One of my MoneySavingExpert.com users struck gold this way: "Worked there ages ago and only paid in for a few years, so wasn't expecting much. Four weeks later, heard there was a £21,000 pension."

4. Find old investments

If you think you've lost an investment, trace for free by contacting the Investment Management Association (www.investmentuk.org ) or calling The Association of Investment Companies (020 7282 5555).

If that doesn't work, there's a £25 service from Unclaimed Assets Register (www.uar.co.uk) that you can use to search 85 financial services companies for pensions, unit trusts, insurance policies and other investments.

5. Find deceased relatives' lost assets too

If a family member has died and you're responsible for the estate, or you're the beneficiary, you may be able to reclaim the above for them too.

You'll need to put their name (as the account holder) on search forms. To get the cash, you'll need their will to prove who the right person to get the money is. If there wasn’t a will, you should be able to get the cash if you’re the rightful heir under intestate rules. More help at www.bba.org.uk/publications/entry/bereaved-customers.

6. Save £1,000s on forgotten direct debits

It sounds cuckoo, but many have regular payments dripping out of accounts for things they don't use or need. If you bank online, spend five minutes today interrogating all direct debits and standing orders – if not, pop into your bank and ask staff for them.

To show the scale, one of my site users helped his sister-in-law check, finding "three mobile insurance contracts she'd forgotten about, payments to OLD gym and others, cutting these saved over £1,000".

7. Reunite yourself with lost Tesco vouchers

Millions of Tesco Clubcard holders lose or forget to use vouchers. You can claw back two years (possibly more) of unused vouchers by logging into Tesco’s Clubcard section. Some find £100s, one told me: "I found £159 worth of vouchers that I had lost. Excellent result." Step-by-step help and the top 10 ways to redeem at www.moneysavingexpert.com/Tescoreclaim

8. Not used it in a year? Flog it

Stock control's a core part of what any shop does to stay profitable. They treat assets as cash, ensuring they’re utilised. We should adopt a similar system. If you've things you've not used or worn in a year, consider flogging them to release the assets.

Selling via www.ebay.com usually pays best, but if you need speed and ease, several sites let you enter details, they offer a price, you post them for free. Up to £150’s possible for old mobiles. Use my comparison tool www.mobilevaluer.com to find the best price per handset (price differences can be huge, eg, £148 to £74 for an iPhone 4 32Gb).

For books, try webuybooks.co.uk or www.Amazon.co.uk's Trade-In section and offload old CDs and DVDs at Musicmagpie.co.uk.

9. Don't lose out on cash every time you pay

When you pay on a credit card, even if it makes no interest from you, the retailer pays the card company a fee. There's a way to get this type of cash in your pocket instead.

Switch to a cashback credit card with a direct debit to repay IN FULL each month, so there's no interest, and effectively this money becomes yours.

The no-annual fee Amex Everyday (americanexpress.com) pays 5p per £1 spent on up to £2,000 within three months, then tiered rates up to 1.25% after. Fail to fully repay and its 19.9% rep APR will wipe any gains. Full list of top cards at www.moneysavingexpert.com/cashbackcards

10. Check down the back of sofas, jackets and bags

No joke, over £40 million of 'lost cash' is allegedly stuffed down the back of cars, sofas and wardrobes. Last time I suggested having a rummage, one of my site users said: "After reading, I thought, 'why not'. Checked a handbag I'd not used since Christmas and found a purse with £80 in it. Very pleased! "

Another reported: "Found $70 in a drawer. Exchange rate's better when I went on hols, so I'm doubly quids in!"