Can I import all the check details for 3 months from desktop to QBO?

It's possible but you will need a 3rd party migration tool.

You can run an Account QuickReport to export your data, JM0073. Let me guide you through the process.

Here's how:

1. Go to the Accountant.
2. Click the Chart of Account.
3. Choose the Account you want.
4. Select Right-click, then run QuickReport.
5. Filter the Date into a 3-month period and then click Customize Report.
6. Click the Filters tab and enter Transaction Type from the search filters field.
7. From the All dropdown click Multiple Transaction Types and choose Check and Bill Payment.
8. Hit OK then OK.
9. Click the Excel dropdown and choose Create New WorkSheet. Then hit Export.
10. Choose .csv as the file type. Then click Save.

Next, open your QuickBooks Online account and follow these steps to import your exported files from QuickBooks Desktop. Here's how:

1. Go Transactions, then Bank Transactions.
2. From the Link account dropdown choose Upload from file.
3. Upload your file then hit Continue.
4. Follow the onscreen instructions.
5. Then click Done.

In addition, you can check out this article to learn how to run basic reports: Run reports in QuickBooks Online.

Let me know if you have any further questions about data migration, feel free to leave a reply. We're here to assist you 24/7.