Spotted a direct debit or card payment you don't remember making on your bank account statement?
Chances are it's a continuous payment authority (CPA). CPAs are used organisations offering a range of services, including home insurance, breakdown cover, payday loans and gym membership.
They allow the automatic renewal of such contracts using your debit card or credit card – without the need for your your authorisation.
The Financial Conduct Authority said: "If you give a company the long number across your debit or credit card and authorise it to regularly take money out of your account, you probably have a continuous payment authority."
So if you miss a letter or email informing you that your contract is up for renewal, and fail to opt out of the auto-renew service as a result, you end up getting and paying the service whether you want it or not.
That's what happened to me recently, when I missed a letter from my home insurance provider The AA.
My home insurance contract was renewed automatically as a result. In one way, this was a blessing as it meant my home was not left without insurance.
But a quick comparison website search reveals that several companies offer similar cover for less than I paid at renewal.
Even The AA itself offered me a policy for the same property that cost £60 less than it charged to renew my contract, illustrating the importance of shopping around for insurance every year.
My statement also showed another payment to The AA, this time for £71.12. And when I called up to query it I was told it was for my breakdown cover, which had apparently been offered free for a year with my original home insurance policy.
In other words, The AA was able to automatically continue my membership contract - even though I have no recollection of being offered breakdown cover with my home insurance in the first place.
Unfortunately, the 14-day cooling off period had ended by the time I noticed the breakdown cover payment. So I was unable to get a refund, even though I have no need of it.
However, the insurer argues that it makes every effort to ensure people are aware their contracts are due to be automatically renewed.
Ian Crowder at The AA said: "We generally write to people about a month before an insurance or breakdown contract is due to end asking them to opt out of the automatic renewal if they do not want it. The information about how to opt out is very clear."
That's why it pays to check your mail, and to keep a close eye on money going into and out of your accounts.
How to avoid the automatic renewal trap
1. Be aware what sort of payment terms you are agreeing to when you take out insurance or a subscription service, for example.
2. Open all mail from companies you have signed up to services with in the past - even if you think it is just marketing junk mail.
3. Keep an eye on your emails - some companies will inform you of plans to auto-renew your contract this way.
4. Check your bank account regularly for any unexpected payments.
5. Query any payments you have not authorised as soon as you spot them: your chances of getting a refund are generally a lot higher if you query the payment within 14 days of it going through.
6. If the company to which you pay a CPA refuses to cancel it, contact your card issuer and cancel the payments that way.