I'm trying to upload .csv files of transactions but every time I do it says the upload failed. Any way round this?

What kind of transaction data do you wish to import? As far as I know, QBSE only imports bank transactions.

It's my priority for you to import bank transactions from .CSV into your QuickBooks Online (QBO), jhamilton-esq.

To upload your CSV bank transactions, let's make sure we choose the correct columns in the mapping stage. QBO will unable to read the data preventing them to upload to your Online account. Here's how:

1. Delete columns you do not need from your CSV to avoid any confusion. The columns that are required by QuickBooks are the Date, Description, and Amount. 
2. Change the names of the columns in your CSV to match the titles in QuickBooks.

Then follow the right formatting in the Common errors for importing bank transactions using CSV article. Once done, try uploading bank transactions from .CSV to QBO again. Just follow the steps and details in the Import bank transactions from .CSV to QuickBooks article. 

To learn more about importing CSV files, check out these articles:

• Import/export CSV files
• Format CSV files in Excel to get bank transactions into QuickBooks

Feel free to visit our Banking page for more insights about managing your bank feeds transactions.

I'd like to know how you get on after trying the steps, as I want to ensure this is resolved for you. Feel free to reply to this post and I'll get back to you. Take care always.