Reviewing my taxes and my mileage was missing many dates for last financial year. Ended up deleting all the mileage logs due to them being wrong. trying to input manually but won't let me add any.

Let me show you how to add your miles in QuickBooks Self-Employed (QBSE), @jacqui850.

You'll just have to make sure to enter all the necessary information like the date, distance, and trip purpose to save the trip.

Here's how:

1. From your homepage, go to the Miles menu. 
2. Click on Add trip. 
3. Set the date, the format should be DD/MM/YYYY.
4. Enter the miles, vehicle and trip purpose.
5. Select Save once you're done. 

See this article for more information on how to add a trip and on how to edit or delete an existing trip: Manually track mileage in QuickBooks Self-Employed.

In case, you're still unable to add any trip, then I suggest clearing your browser's cache. There are times that the piled-up cache in your regular browser caused this unusual behaviour when trying to add one. Here's the clear cache and cookies to fix issues when using QuickBooks Online article for detailed guidance. 

You can also use other supported browsers (Firefox, Google Chrome, Safari 11 or newer, Microsoft Edge) if the steps above didn’t work.

To know more on how to use the QBSE mobile app to automatically track your business miles, see this reference: Automatically track mileage in QuickBooks Self-Employed. In case you'd encounter any issues, here's how to fix mileage tracking issues in QBSE for Android or fix mileage tracking issues in QBSE for iOS.

I'm always here if you still have issues with adding your trips in your account. Take care and have a great rest of the day!