What do I do with an Invoice a customer refuses to pay?

We'll have to write off bad debts, RebeccaH.

Let me guide you how:

First, let's 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: 

I'm just a post-away if you have other concerns about bad debts. Keep safe!