There can be several reasons why you may not recognise a transaction on your statement, and they’re not always suspicious.
A joint account/secondary cardholder
if you have a joint account or have authorised an additional cardholder on your account, check whether this person recognises the transaction. If it’s a card transaction, your statement will show the last four digits of the card used to make the transaction.
A company uses a different name
Businesses and retailers can trade under a different trading name from the one you know them as or were expecting to see on your statement.
A regular payment
A regular debit or charge card payment (that is not a standing order or Direct Debit) for a subscription to a service that you previously agreed to. For example, a monthly subscription such as Netflix
A pre-authorisation
Sometimes when you pre-book something, like a hotel room or a rental car, the firm will reserve an amount of money on your card. This will either be released or absorbed into the final cost when it’s known.
A free trial has expired and you’re now signed up for the full product
If you recently signed up for a free trial (for example Amazon Prime), check whether it has expired as often a company will automatically start taking a monthly payment once the free trial has expired.