How can I reflect 50% of the amount due on an invoice when I initially send the invoice to a customer?

Thank you for posting here in the Community, @larroliga.

 I’d be happy to share with you about Progress invoicing in QuickBooks Online.

 Progress invoicing allows you to send an invoice to a customer for partial payments. It is also known as progress billing. You’ll receive multiple partial payments throughout the timeline of one job instead of one full payment at the end.

To send progress invoices, you need to turn on Progress Invoicing in QuickBooks Online.

Here’s how:

1. Log in to your QuickBooks Online account and click the Settings icon, and select Account and Settings.
2. Select the Sales tab.
3. In the Progress Invoicing section, choose Edit. Then, select the Create multiple partial invoices from a single estimate checkbox.
4. Once done, click Save and Done.

Now you can create multiple invoices from your estimates. You can follow the steps below:

1. Go to the Sales menu and select All Sales. Then, find the estimate on the list.
2. Select the Create invoice from the Actions column. You can also open the estimate and select Create invoice. Then, decide how much you want to invoice for. 
3. Choose the Create invoice. You can charge for a percentage or a specific amount. If you choose a custom amount for each line, enter a specific amount for each item on the invoice.
4. Fill out the rest of the invoice and select Save and new or Save and close.

Connect an estimate to a new invoice.

1. Select the + New icon and then choose Invoice.
2. Select your customer from the drop-down menu. If the customer has an open estimate, QuickBooks will open the Add to Invoice sidebar.
3. Find the estimate in the sidebar and select Add.
4. Decide how much you want to invoice for, and select Copy to invoice.
5. Fill out the rest of the invoice.
6. Once done, select the Save and new or Save and close.

You can use this article about the progress invoice template and how to make it as default: Send progress invoices.

Also, please refer to this article for additional details on how to customize the report to focus on the data that you want to view: Customize reports in QuickBooks Online.

Please know that you're always welcome to post if you have any other concerns. Wishing you and your business continued success.