For each PayPal transaction, a fee will be deducted from the amount your customer pays you.
When accepting payments with PayPal, payments fees for the United Kingdom start roughly at 3.4% + 20p per transaction. When accepting PayPal payments from international cards, including American Express, international fees can be as much as at 3.9% + fixed fee which PayPal sets and varies by country. Make sure to read the PayPal Express Checkout fees help article for a complete breakdown of all domestic and international transaction fees. Please note that PayPal collects all payment transaction fees.
If you process a lot through PayPal, you may be eligible for reduced fees. Get in contact with PayPal if this applies to you.
Within your PayPal Business account, you have access to payment history, recent payments and payment details, including each transaction fee. In the notes section for each payment, you can reference the Invoice2go invoice number.