How do I recover all the transactions during a long period my bank was not syncing with QB?

Download the bank statement file from your bank and import it manually to your QBO account. Another option, utilize MT Online as a workaround. It is designed to import into any bank or credit card in QuickBooks Online, so there is no specific setting needed. 

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Hi, gannonstudios.

There are two ways on how to bring the transactions into your QuickBooks Online account.

Since there were six months worth of transactions needed to be uploaded, manually doing it is one of our options. After you get the transactions from your bank, review the file format, and then you're good to upload the items. Here's how:

1. From the Banking tab, select Banking.
2. Select the blue tile for the account you want to upload the transactions into.
3. Click the Link account drop-down and select Upload from file.
4. Select Drag and drop or select files and then Continue.
5. In the QuickBooks account dropdown, select the account you want to upload the transactions into. Then select Continue.
6. Follow the onscreen steps to match the columns and click Continue.
7. Select the transactions you would like to import. Click Continue again.
8. Select Yes and then Done.

The other way to upload the items is by using a third-party application. There are apps that can upload six months worth of transactions. You can click this link to search for an app: QuickBooks Online Apps.

From there, you can categorize the transactions. Here's an article as your guide: Categorize transactions.

I'll be around whenever you need help with the process.