Once you have selected your Accounts Application and have specified your Import File, you can then click the Test button.
As you can see from the above example, the system has read the exported file, it contains four columns of data but only three are used by the system - these are highlighted in yellow.
Anything highlighted in red has been spotted as an error by the internal checking systems and will prevent you from Importing the data and Submitting it to the HMRC.
NOTE:
Different import routines will have different number of columns, etc, so your screen may look slightly different to the one shown above. But in a nutshell you should find that boxes 1 - 9 are automatically shown.