Trying to invoice the unpaid retention of an invoice I have to invoice 12 months later. Can I make new invoice that will connect to the unpaid invoices in the project?

Let me help you create a new invoice that will connect to the unpaid invoices in Project, r-jamous.

We can add the existing invoices to projects before they’re linked to a payment. Then, choose the Retainer or Deposit item in the Product/Service column to track as retainer. If you haven't created one, just follow the steps and details in the Record a retainer or deposit article to record a retainer or deposit in QuickBooks Online (QBO). Then, add the unpaid invoices by following the steps below: 

1. Click the Sales tab
2. Select the Invoices tab.
3. Find and select the unpaid invoice.
4. Hit Edit invoice.
5. Select the Customer dropdown. Then select the project. 
6. In the Product/Service column, choose the Retainer or Deposit item. 
7. Press Save.

Then, you can add a paid invoice to your project. To learn more about this one, see the Add existing invoices to QuickBooks Online Projects article. Feel free to visit our Sales and customers page for more insights about managing your company's income and customers.

I'd like to know how you get on after trying the steps as I want to ensure this is resolved for you. Just reply to this post if you are also referring to something else and I'll get back to you. Take care always. 

Thanks. But I do not think this solves my problem.

Every invoice I have for a project has been partially paid and generally a sum of 5% is left over. After 12 months I can claim the final unpaid portion of the invoices. I want to know if I can do an invoice that is similar to a statement showing the invoices, and the remaining sums, that need to be paid. Once I get paid I will receive the payment on the "statement" which will show that the initial invoice as paid. In the picture I have high lighted the sums that I would like to compile in a new invoice that is linked to these invoices when I receive payment

Thanks for coming back to this thread, r-jamous.

Allow me to join the conversation and provide additional information about invoices.

Currently, the option to create an invoice that shows the remaining sums or unpaid retentions is unavailable in QuickBooks Online. I can see how this would help you in tracking your receivables. To help improve your experience in QuickBooks, I recommend sending feedback to our Product Development Team.

Your ideas and suggestions will guide us in determining what features to add and how we can make the product better for you. Here's how to do it:

1. Sign in to your QBO account.
2. Click the Gear icon at the top, then choose Feedback.
3. Enter the new features you would like us to add in the description box.
4. Select Next to submit feedback.

In the time, you'll want to consider visiting our QuickBooks App Center or go to the Apps menu to find a third-party invoicing app that best suits your business needs. I'll show you how;

1. Sign in to your QBO account.
2. Select Apps from the sidebar menu, then go to the Find Apps tab.
3. Enter a keyword in the search bar or Click the Browse category button to filter the results.

Additionally, you might want to check this article that will help you in personalizing your invoices: Customize sales forms.

Let me know in the commend section if there's anything else that I can help you with. I’ll be more than happy to assist you again. Have a great rest of the day.