How to enter a transaction for future payment?

This is just the place to get the answers you're looking for, @mrairnyc.

There are two ways to record sales transactions in QuickBooks: Invoice and Sales Receipt. An invoice is used when your customer agrees to pay you later. Once you send an invoice, it becomes part of your Accounts Receivable. You can set up terms to indicate how long the customer has to pay. A sales receipt is used when your customer pays you on the spot for goods or services.

Since you've mentioned that you need to track the amount of $400 as Accounts Receivable, I'd suggest creating an invoice for the contract amount of $1,000. Then, receive the partial payment of $600. This way, you'll get a remaining amount of $400 in Accounts Receivable.

Here's how to receive a partial payment:

1. Click the +New icon.
2. Choose Receive Payment.
3. Enter the customer's name.
4. Select the invoice.
5. In the Amount received field, enter the partial payment amount of $600.
   
6. Click Save and close.

Once done, the status of the invoice will automatically change to Partial. You can send another invoice once the work is done. It will only show the remaining balance due. To get in-depth information about invoice payment, you can refer to this article: Record customer payment in QuickBooks Online.

Furthermore, QuickBooks Online also offers progress invoicing. It lets you split an estimate into as many invoices as you need. This is a great tool for tracking projects to keep it organized and connected from start to finish. For more information, check out this link: Set up and send progress invoices in QuickBooks Online.

Visit me again here in the Community should you need further assistance in keeping a close eye on your projects in QuickBooks Online. I'm always available to help. Have a good one!