I have received a single payment for a number of invoices, they have deducted a charge for a training course. How do I show this when I match up invoices with payments

Hello there, dave193. 

You can edit the invoice and add another line item for the training charge to have the same amount of your transaction and also in your bank. 

Additionally, you can take a look at these pointers to help guide you more in managing your invoice in Quikcbooks: Add service fees manually to invoices.

That's it. Let me know if there's anything else I can do. I'm still here to help you further. Just add a comment or mention my name. Wishing you all the best!