In some cases, an amount of €1/£1/$1 may be shown in the Payments tab on your account, as a Pending Transaction. It's usually related to a merchant's attempt to verify the validity of your payment card.
When making a payment, a temporary authorization is put on your card, for a nominal amount. Merchants use this to confirm that your payment account is active and has the funds available for purchases.
For example, in the UK, you may see a temporary £1.00 authorization hold. If you live in another country or region, you might see a different amount in the currency of your region.
Paypal might also check the validity of your card with a small authorization.
Authorization holds should expire after a short time (18 days maximum) just like any transaction attempt.