How can I input work as I'm going and then invoice at the end of the month?

Hello, @kimbelle-gmail-c.

I’m here to make sure that you can successfully input your work in QuickBooks Online.

You can input your work anytime and send it after a month. You can do it by simply following the steps.

Here’s how:
1. Select + New and then select Invoice
2. Select Add product or service from the ▼ dropdown to add one. If you're ready to send your Invoice after a month, select the Receive Payment ▼ dropdown. From there, you will see a few options for sending the invoice.

•        To email the invoice to your customer, select Email. Make any edits to the Email body field and then select Send invoice. 
•        To print a paper invoice, select Print and download. 
•        To send your customer a link to their invoice through SMS or a messenger service, select Share link. Then select Copy link and paste it in your SMS or messenger service.

You can click these articles for more information:

• Estimate into an Invoice
• Create Invoice in QuickBooks Online

If you run into any trouble along the way, just let me know. I’m always around to help you. Wishing you more success in your business. Have a great day!