Hello judy-sspm-co-za, it's nice to hear from you!
I'll share some details about voiding an invoice in QuickBooks Online.
When voiding an invoice, it'll not automatically send a credit to your customer. However, you'll notice some changes in your customer data within your QuickBooks Online (QBO) account. It keeps the invoice number and lists it in reports but changes the amounts to zero.
Still, you can manually send the voided invoice to your customer (if necessary). Here's how:
Go to the Sales menu.
In the Sales tab, find the voided invoice and click the drop-down arrow under the Action column.
Click Send and enter their email address. You can include a message that this is voided invoice.