Tesco shopper? Today is your LAST CHANCE to spend or extend £18 million of expiring Clubcard vouchers

Below is everything you need to know. For more on getting the most out of Tesco's loyalty scheme, see our Clubcard reclaim and boost guide.

How to check if your Clubcard vouchers are due to expire – and find missing vouchers

Clubcard vouchers are only valid for two years from the date they were issued (unless you're able to extend them – see how to extend them below). If you're unsure when yours expire and you've still got them in paper format, check the date on the actual vouchers.

If you've lost your paper vouchers, or are unsure whether you had any in the first place, you can check on the Tesco Clubcard site or app. Here's how:

• To check online, go to the Tesco Clubcard website, select 'Clubcard account' and then 'Vouchers'. You'll need to be registered for a Tesco.com account and must know your Clubcard number, which is printed on Clubcards and Clubcard key fobs. You should then be able to see a table listing your available vouchers and their expiry dates.

• To check on the app, open it up (if you don't have it, you can download it for free through the Apple App Store or Google Play Store), then go to 'Clubcard' and then to the 'Vouchers' section.

Want to double the value of your vouchers? Spend them at one of Tesco's 'Reward Partners'

Once you've found your vouchers, you can spend them online at Tesco using the code provided – or if you plan to spend them in store, you can print your vouchers or scan the barcode available on the app at the checkout.

Alternatively, you can double the value of your vouchers by spending them at Tesco's 'Reward Partners', such as Cineworld, Pizza Express and Thorpe Park. For example, 500 points are usually worth £5 to spend at Tesco – but if you exchange your vouchers for codes to spend with a Reward Partner, 500 points become £10.

Clubcard holders were previously able to swap vouchers for triple their value, but last year Tesco slashed this to double their value.

For more on how to make the most of your points, see our Boost Clubcard vouchers guide.

If you don't want to spend them, try to extend your Clubcard vouchers

If your Clubcard vouchers are due to expire and you don't want to use them yet, you may be able to extend the usual two years' validity for another two years.

Technically, under the Clubcard T&Cs, Tesco can refuse a Reward Partner order if it decides you're trying to game the system by redeeming vouchers just to extend their validity – but we tested the trick at MSE Towers earlier this month and it worked just fine.

Here's how it works – remember you'll need to extend your vouchers by 11.59pm on Thursday 29 February:

• Make a small purchase on the Tesco Clubcard Rewards page (not in store or on other Tesco pages) or donate to one of its partnered charities. The remaining balance is credited back to your Clubcard account as points. So if you spend 50p using a £5 Clubcard voucher, you'll get 450 points back (worth £4.50).

• You can then swap your points for vouchers manually or wait for them to be converted with your next statement. The expiry date for these new vouchers will be two years in the future.

• There's no minimum spend, but the aim is to shell out as little as possible. A good option might be a 50p restaurant voucher (worth £1 at your chosen restaurant).

You'll need to do this for each individual voucher, so it's worth weighing up if it's actually worth it for smaller denominations. For example, if you've a £10 voucher it could be worth it. If you've got a handful of £1 vouchers, maybe less so.