ReceiptPal only accesses the camera when you are taking pictures of receipts.
If you use a Samsung mobile device, a background permission related to the Samsung App Permission Monitor may show that ReceiptPal is using your camera while the app is closed. The App Permission Monitor detects that ReceiptPal is running in the background for other purposes (e.g. receiving messages from ReceiptPal), sees that you have granted camera permissions to ReceiptPal, and alerts you that ReceiptPal might be using your camera when it is not.