The P11D Organiser allows you to preview your reports 'inline' within the browser - that allows you to streamline the checking process.
Some users have found issues with the preview, and see a screen similar to the one below:
This is likely due to the way your browser has been configured to handle PDF files (it is configured to download them rather than display them).
You can correct this behavior from the setting on your browser- although very similar in the way they work, the route to find this setting is different in Google Chrome and Microsoft Edge.
Chrome
You need to select settings from the three little dots in the upper right corner:
Then navigate as follows: Settings > Privacy and Security > Site Settings > Additional content settings > PDF Documents > Default behavior. You probably then see the setting as below - this will cause issues:
For the system to preview reports, you need this set to Open PDFs in Chrome
Edge
You need to select settings from the three little dots in the upper right corner:
Then navigate as follows: Settings > Cookies and site permissions > PDF documents. You will likely see the setting as below:
The 'Always download PDF files' needs to be OFF for the system to preview reports.
Organisation Control
If you find you are unable to edit this setting, you will need to raise this with your IT team, as it is something that they have taken control of.