I've got you covered, @DDWorks. Let's work this out together so you can get back on track.

The option to copy transactions from one company file to another is possible for QuickBooks Desktop Premier and Enterprise Accountant versions only. If you're using an accountant version, here's how to transfer or copy your customer's transactions to your original file: 

First, you'll need to set the Preferences appropriately to allow the export.

1. Disable the use of Account Number.
   1. From the Edit menu, choose Preferences.
   2. Select Accounting and choose the Company Preferences tab.
   3. Uncheck Use account numbers, then select OK.
       
2. Disable Sales Tax.
   1. From the Edit menu, choose Preferences.
   2. Select Sales Tax and choose the Company Preferences tab.
   3. In the "Do you charge sales tax" section, select No, then choose OK.

Next is to create a Custom Transaction Detail report. Here's how:
 

1. From the Reports menu, choose Custom Reports and select Transaction Detail.
2. Select Customize Reports and modify the reports.
3. To run the report, select OK.
4. Memorize the report and save it as PDF if desired.

After that, you can now export the report in excel.

1. While the report is open, select the Excel drop-down.
2. Choose to Create New Worksheet.
3. Select a new workbook, then choose Export.

Lastly, enter your transactions by batch in QuickBooks Desktop.
 

For a more detailed guide, refer to this article: Copy multiple transactions from one company file to another. 

I also encourage you to visit our QBDT Help page. From there, you can browse articles or get some ideas from other QuickBooks users and experts. This way, you'll get more insights that can help you with your accounting tasks.

Feel free to post a reply if you have additional questions about copying transactions from one company file to another. Take care and have a good one!