How do I deduct money from an invoice?

Thanks for getting back to us laurentofield97- there's no specific feature for customer discounts in QuickBooks Self-Employed, instead, you can add an additional line on the invoice for this by selecting 'Add work', in the description enter discount (or how you wish this to appear) and enter the discount amount with a minus figure, i.e. - 5.00. You'll then see this deducted from the total of the invoice. 🙂