Error with calculation "more than one column"

[Anonymous]

Hello All,

I am very new to Power BI and I am trying to create some calculations by using the formula PREVIOUSMONTH. However, every time I tried using different data, I kept getting the same error: "The visual calculation 'Formula' has a syntax or semantic error at line 1, position 39 reported by Analysis Services. 'A table expression containing more than one column was specified in the call to function PREVIOUSMONTH, which is not supported.

Here is my table and my formula : 

Calculation = CALCULATE([Count of Document Number1],PREVIOUSMONTH([Month]))

I am trying to create a formula to show the value from the prervious month.

Thank you in advance for your help

[3CloudThomas · Accepted solution]

The PREVIOUSMONTH DAX function needs a date column, not a column with month values.

PREVIOUSMONTH function (DAX) - DAX | Microsoft Learn