Can I back date transactions that happened in 2023 if I just purchased quick books in 2024?

I'll share some information when you're using QuickBooks Online (QBO), Hope.

Yes, you're right. With QuickBooks, you can record your 2023 transactions even if you've just purchased QBO this 2024. You'll just have to make sure to enter the correct date and save the transaction so that when running reports, you'll be able to access the data. 

To give you walkthrough guides through the process, and check out some of our videos to learn more of our products, I've added this link for you: Getting Started When Using QuickBooks Online.

If there's anything else that you want us to help with, let us know so we can get back to you as soon as possible. We're here to ensure we address all your concerns. Have a nice day ahead. Thanks for choosing QuickBooks.