I am figuring out how to enter the disallowed amount from insurance. Ex, I charge $200, insurance pays $100, and client pays $25, how do I account for the $75?

I'll help you account for the disallowed amount from insurance, PJBluenose.

To put the disallowed amount on the invoice, I agree with the steps you provided and adding the negative amount to close it out if you'll charge this to your customer. However, if you're not collecting it from them, you can write off the $75. Here's how:

First, create a bad debts expense account.

1. Go to Settings and choose Chart of accounts.
2. Click New to create a new account. Then, from the Account Type dropdown, select Expenses.
3. From the Detail Type dropdown, click Bad debts.
4. In the Name field, enter "disallowed amount" and hit Save and Close.

Then, create a bad debt item.

1. Go to Settings and choose Products & services.
2. Click New and then Non-inventory.
3. In the Name field, enter " disallowed amount.
4. From the Income account dropdown, select Bad debts and hit Save and Close.

Create a credit memo for the disallowed amount.

1. Click +New and choose Credit memo.
2. Select the customer from the Customer dropdown.
3. In the Product/ Service section, click Bad debts.
4. In the Amount column, enter the $75 to write off.
5. In the Message displayed on statement box, enter "disallowed amount" and hit Save and Close.

Lastly, apply the credit memo to the invoice.

1. Click +New. Then, under Customers, select Receive payment.
2. From the Customer dropdown, click the appropriate customer.
3. From the Outstanding Transactions section, select the invoice.
4. From the Credits section, click the credit memo. Then, hit Save and Close.

You can also consult an accountant to help you handle this. 

Moreover, I'll add this article to help you record, edit, and delete expenses: Enter and manage expenses in QuickBooks Online.

Comment below if you have further questions about tracking your disallowed amount from insurance. I'll be here to assist you. Stay safe!