Buy-now-pay-later has become a fast-growing industry worth £2.7bn, quadrupling in use between 2018 and 2020.It allows customers to pay the full amount for their things at a later date or pay in interest free installments over a period of time.An estimated 14 million people used the likes of Klarna, ClearPay, LayBuy and Afterpay in the UK last year, according to Citizens Advice. But for those who did not select Buy Now Pay Later at the checkout, you may be wondering why these company names still sometimes show on your bank statements or online banking apps.One reason is that some retailers use BNPL to manage their checkouts, so it shows up as the payment method even when you pay up front. You can check with the retailer to make sure it was a normal card purchase if you are worried.Another reason could be fraud, and you may have been a victim of identity theft. In this case you should contact your banks, the BNPL company, and Action Fraud, the UK’s national fraud and cyber crime reporting centre.They also recommend applying for protective registration through CIFAS, a national non-profit fraud prevention community.According to Citizens Advice, of the estimated 14 million users in the UK last year, 39% used buy now pay later without realising, so you might have accidentally opted for it without realising.It may have been pre-selected as the default payment option. Make sure to pay attention when you are about to checkout.