Tomorrow is so-called "Cyber Monday", a peak shopping day in the run-up to Christmas, with six million UK consumers predicted to rack up a total bill of £556 million shopping online.

We are set to spend almost £10 billion in December, yet most people are unaware that if you use your credit card you have a guaranteed insurance against disappointment.

Known as Section 75 protection, it obliges your card provider to reimburse you against any goods or services worth more than £100 which are not as described, which are faulty, which fail to arrive, or where the company goes bust or is in some other breach of contract.

A survey by comparison website money.co.uk found one-quarter of credit card holders had never heard of the protection, while 12% believed any protection came only with a fee-paying card or as a standalone insurance.

However, over the last three years, 21% of the UK's 30 million credit card users have made a claim under Section 75 of the 1974 Consumer Credit Act, with 77% of claims upheld and paid out.

Hannah Maundrell at ­money.co.uk said: "Even if the card account is no longer open, the claim is still valid in the eyes of the law. For consumers who feel they are being fobbed off by their credit card provider in the event of a rejected claim, the Financial Ombudsman Service is at hand."

However, the protection is far from foolproof. It is only valid for single items costing £100 to £30,000 - so if you buy two flights which each cost £90, that will not be covered even though the total is more than £100. But if you are buying a kitchen costing £15,000 and pay a £150 deposit on your credit card, then you will be covered.

You won't be covered if you buy through an intermediary, such as a travel agent. And forget Section 75 if you use Amazon or PayPal. Money.co.uk said: "These organisations have their own legal protection in place, but it's not to the same standard."

Scots plan to spend an average £350 on Christmas, according to cash-back website TopCashback.co.uk. It says 16% of men and 13% of women admit to putting the festive costs on to a credit card, but two-thirds of Scots have set themselves a budget - with more than half of women say they make their own gifts and "re-gift" unwanted presents to save money.

Rival cash-back site Quidco says 81% of those in Scotland are part of some kind of reward or loyalty scheme and three out of 10 will use rewards and points to buy gifts.

Independent research claims the average annual saving for those who use discount schemes mounts up to £1200 a year. Yet more than 20% of men believe cash-back and voucher sites are "too much hassle".

Quidco said YouGov research suggests the average UK household spent £822 on Christmas last year, adding that the average family earns more than £780 a year with Quidco - though its research also found 23% of Scots admit having bought something they didn't really need just to earn loyalty points.

The over-50s are the most likely to be missing out on discounts, with 62% never using online vouchers or cash-back offers, according to over-50s website Silversurfers.com. It is launching Silvercard+, a discount card offering exclusive deals from retailers, travel firms, airlines, hotels, and tech and entertainment companies, with a substantial increase in deals promised in the new year. The first 100,000 to sign up will have a free card for six months, then it is £1 a month.

Finally, when shopping online, keep an eye on your security, advises Livingston-based IT specialist EMC.

It recommends:

l Don't link everything to the same email address - use multiple email accounts to keep banking and online payments separate from social media accounts such as Facebook and Twitter.

l Make passwords difficult - too many of us use the same password for everything. Change your password before embarking on online shopping.

l Shop at work if you can - if you can use your computer at work, in your lunch hour, it could be more secure and less vulnerable than a home or public computer. Don't carry out financial transactions in public places like internet cafés, hotel receptions and airport kiosks.

l Keep personal information personal - don't reveal personal or financial information in an email. Protect your date of birth as it's a widely requested security question. Make sure you set up your security settings correctly on any social networks, and don't give away confidential information through posts and messages.

l Pay close attention to URLs - malicious websites may look identical to the real site, but the URL may use a variation in spelling or a different domain.

l When in doubt, throw it out -links in emails, tweets and online advertising are a way for cybercriminals to compromise you. If it looks suspicious, mark as junk email.