I'd be pleased to help you sync your missing transactions in QuickBooks Online, _bradhall.

When syncing your bank for the first time, QuickBooks will automatically download your most recent or 90 days' worth of transactions. To import your missing data, you can use our WebConnect feature.

Here's how: Step 1: Pick a start date:

1. In QuickBooks, go to the Accounting menu and then select Chart of Accounts.
2. Look for the bank or credit card account you want to upload the transactions into.
3. Click View register.
4. Find and write down the date of the oldest transaction. Usually, the oldest transaction is the opening balance.

Step 2: Get transactions from your bank:

1. Sign in to your bank or credit card’s website.
2. Follow your bank’s instructions for how to download CSV files of your transactions to your computer. Every financial institution has different steps. For Bank of America, Chase, and Wells Fargo.
3. Check the date range for the download. It should be at least one day before the date of your oldest transaction.
4. Download your transactions. Save the file somewhere you can easily find it, like your computer's desktop.

For other steps, you can refer to this article (proceed to Step 3): Manually upload transactions into QuickBooks Online. On the same write-up, you'll find links on how to set up bank rules as well as reconciling your account.

Once imported, I recommend editing, assigning, and categorizing your transactions. Also, you can match them to the existing entries in the software. Just go to the For Review tab from the Banking menu. Doing so will help you ensure the accuracy of your financial records.

I'm only a post away if you have any questions about this topic or anything else you need in QuickBooks. Have a wonderful day! Take care.