Error-cannot-mix-aggregate-and-non-aggregate comparison or results in 'IF' expressions

Hi Team,

I have encountered below error while creating a calculated field when I am dividing with [Sum_of_INC] /COUNTD(USERS). I have also tried creating a separate Calculated Field but it still errors out. Could you please advise me on this?

"Error-cannot-mix-aggregate-and-non-aggregate comparison or results in 'IF' expressions"

I have used a calculated field with below formula

{ Fixed [Date ],[Name], [LOB]:

SUM(

IF  

[TYPE] = 'CS' 

AND [LOB]='XYZ'

THEN

[Sum_of_INC] /COUNTD(USERS)

ELSE NULL END)

}

Thanks & Regards,

Anand