Hello there, @I-Already-Had-A-Username.

Let me clarify things about migrating your QuickBooks Desktop (QBDT) company file to QuickBooks Online (QBO).

You're correct that you have to condense your QBDT file up to 750,000 targets so you can export them to QBO seamlessly. Here's an article for your guidance: Condense your QuickBooks Desktop file for import to QuickBooks Online.

Furthermore, the 750,000 target limit is only for the migration process to QBO. After moving your data, you can create as many transactions as you need. The only limitation in QBO is the usage limits of a specific number of things, like how many billable users, chart of accounts, classes, locations, and tags you can add to QuickBooks.

Moreover, you have two options when you have reached your usage limit and cannot add more items, such as users or accounts. You can either upgrade your subscription or reduce your usage. Visit this article and scroll down to the What happens when I reach my limit? section for more details on reducing your use: Learn about usage limits in QuickBooks Online.

Nonetheless, if you use advanced features (such as advanced reporting and advanced inventory), we recommend starting fresh because some of your data won't move to QBO. Check out this article for reference: Move your QuickBooks Desktop file to QuickBooks Online.

Don't hesitate to reply below if you have other questions about migrating your company file to QBO. We're always ready to help. Have a great day!