Do you mean that you have sold things on eBay in the last billing period and you have now been charged for the month's fees?

That invoice would be in your messages and in your Seller's account.

Most have automatic payment of their fees set up. so eBay charge you, send you an invoice (in my case on the 30th of the month telling me payment will be drawn btwn the 14th and 17th) and it gets automatically paid by PayPal.

This includes the whole month's fees from eBay - FVF's any listing fees etc