then I got sent a format from the Quickbooks agent which uploads successfully but doesn't include any of my destinations and when I try to add different dates for my different monthly reports it removes half of them as duplicates.
I tried speaking to MileIQ to see if they can send me a straight CSV format for Quickbooks but apparently that is only available to US customers. So I'm pretty stuck on what I can do here any advice would be appreciated.
Our product engineers are currently investigating about the 400 OK error when importing miles into QuickBooks Self-Employed. They are working to identify the cause and looking for a resolution to this issue.
I'd suggest getting in touch with us again so we can add your account to the notification list. Updates are sent via email. To contact support, check out this link.
Meantime, you can add your miles manually. Let me show you how:
Select the Miles menu and click Add trip at the upper-right.
Enter the distance in the Add miles field.
Add the details and select Save.
You can also check out these articles that will help you handle and record trips:
Other users here might be able to share their working sample file from MileIQ. While waiting for them to share it, I have steps you can do to fix the error message when uploading the file.
A browse cache issue might be preventing you from uploading the CSV file. This happens if the webpage's cache data is corrupted. To confirm this, let's use an incognito window to upload your file. Shortcut keys:
Chrome - press CTRL + Shift + N
Mozilla Firefox - press CTRL + Shift + P
Safari (newer versions) - press Command + Shift + N
If you're able to upload the file successfully, go back to your regular browser and clear the cache (article is for QuickBooks Online but the same steps apply for Self-Employed) to prevent the issue from happening again. Once done, close out your browser windows to complete the process.