A customer refuses to pay several job invoices that total over $8k after being informed i will no longer be doing business with them. How do i get them to pay?

Welcome to the Community, @Mablack8888.  

I'm here to help you manage unpaid invoices in QuickBooks Online (QBO).

First, We'll have to write off bad debts and run the Accounts Receivable Aging Detail report to review other invoices or receivables that should be considered as bad debt.

Second, we'll have to create a bad debt expense account. 

1. From the Accounting tab, select Chart of Accounts.
2. Click New.
3. On the Account Type field, select Expenses.
4. From the Detail Type, select Bad debts.
5. In the Name field, you can enter Bad debts.
6. Select Save and Close.

Afterward, let's create a bad debt item.

1. Select Products and Services, from the Sales tab.
2. Click New.
3. Select Non-inventory.
4. Give it a Name.
5. From the Income account drop-down, select Bad debts.
6. Select Save and Close.

Then, let's create a credit memo. You can enter Bad Debt as the Message displayed on statement.

Lastly, we'll have to link the credit memo to the invoice. I've added this reference for more information about the process: Apply the credit memo to the invoice.

When you're ready to reconcile the statements, you can check this guide: 

Let me know if there's anything else you need or if you have follow-up questions about invoices. Wishing you all the best!