Access Report parameter prompted 3 times?

If the queries are independent then the parameters are independent too.
You can use a form to launch your report and add the parameter as a textbox on the form.  Then both queries can refer to the same textbox instead of your current parameter field.

use your version of ..
Forms!formname!textboxname
in both queries.

If you are getting prompted twice for what you believe to be the same parameter it implies you have used different spellings in the two instances.

I've added a form named ReportCode and textbox named RptCode, I've put [Forms]![ReportCode]![RptCode] in the query column, now it prompts me 3 times with Forms!ReportCode!RptCode in the Enter Paramater Value prompt?

Is the form open?

Please post the sql view of each of your queries.

PARAMETERS [Forms]![ReportCode]![RptCode] Text ( 255 );
SELECT [R12 Monthly Unique].Description, [R12 Monthly Unique].Rpt_Code, [R12 Monthly Unique].Frequency, [R12 Monthly Unique].U1, [R12 Monthly Unique].U2, [R12 Monthly Unique].U3, [R12 Monthly Unique].U4, [R12 Monthly Unique].U5, [R12 Monthly Unique].U6, [R12 Monthly Unique].U7, [R12 Monthly Unique].U8, [R12 Monthly Unique].U9, [R12 Monthly Unique].U10, [R12 Monthly Unique].U11, [R12 Monthly Unique].U12, [R12 Traffic].R1, [R12 Traffic].R2, [R12 Traffic].R3, [R12 Traffic].R4, [R12 Traffic].R5, [R12 Traffic].R6, [R12 Traffic].R7, [R12 Traffic].R8, [R12 Traffic].R9, [R12 Traffic].R10, [R12 Traffic].R11, [R12 Traffic].R12, [R12 Traffic].D1, [R12 Traffic].D2, [R12 Traffic].D3, [R12 Traffic].D4, [R12 Traffic].D5, [R12 Traffic].D6, [R12 Traffic].D7, [R12 Traffic].D8, [R12 Traffic].D9, [R12 Traffic].D10, [R12 Traffic].D11, [R12 Traffic].D12, Recipients.CountOfRpt_Code AS M, IIf([Frequency]<>"Monthly","*",IIf([U1]<1,"*",IIf([M]<1,"*",Round(([U1]/[M]),2)*100 & "%"))) AS Z1, IIf([Frequency]<>"Monthly","*",IIf([U2]<1,"*",IIf([M]<1,"*",Round(([U2]/[M]),2)*100 & "%"))) AS Z2, IIf([Frequency]<>"Monthly","*",IIf([U3]<1,"*",IIf([M]<1,"*",Round(([U3]/[M]),2)*100 & "%"))) AS Z3, IIf([Frequency]<>"Monthly","*",IIf([U4]<1,"*",IIf([M]<1,"*",Round(([U4]/[M]),2)*100 & "%"))) AS Z4, IIf([Frequency]<>"Monthly","*",IIf([U5]<1,"*",IIf([M]<1,"*",Round(([U5]/[M]),2)*100 & "%"))) AS Z5, IIf([Frequency]<>"Monthly","*",IIf([U6]<1,"*",IIf([M]<1,"*",Round(([U6]/[M]),2)*100 & "%"))) AS Z6, IIf([Frequency]<>"Monthly","*",IIf([U7]<1,"*",IIf([M]<1,"*",Round(([U7]/[M]),2)*100 & "%"))) AS Z7, IIf([Frequency]<>"Monthly","*",IIf([U8]<1,"*",IIf([M]<1,"*",Round(([U8]/[M]),2)*100 & "%"))) AS Z8, IIf([Frequency]<>"Monthly","*",IIf([U9]<1,"*",IIf([M]<1,"*",Round(([U9]/[M]),2)*100 & "%"))) AS Z9, IIf([Frequency]<>"Monthly","*",IIf([U10]<1,"*",IIf([M]<1,"*",Round(([U10]/[M]),2)*100 & "%"))) AS Z10, IIf([Frequency]<>"Monthly","*",IIf([U11]<1,"*",IIf([M]<1,"*",Round(([U11]/[M]),2)*100 & "%"))) AS Z11, IIf([Frequency]<>"Monthly","*",IIf([U12]<1,"*",IIf([M]<1,"*",Round(([U12]/[M]),2)*100 & "%"))) AS Z12
FROM ([R12 Traffic] LEFT JOIN [R12 Monthly Unique] ON [R12 Traffic].Rpt_Code = [R12 Monthly Unique].Rpt_Code) LEFT JOIN Recipients ON [R12 Traffic].Rpt_Code = Recipients.Rpt_Code
GROUP BY [R12 Monthly Unique].Description, [R12 Monthly Unique].Rpt_Code, [R12 Monthly Unique].Frequency, [R12 Monthly Unique].U1, [R12 Monthly Unique].U2, [R12 Monthly Unique].U3, [R12 Monthly Unique].U4, [R12 Monthly Unique].U5, [R12 Monthly Unique].U6, [R12 Monthly Unique].U7, [R12 Monthly Unique].U8, [R12 Monthly Unique].U9, [R12 Monthly Unique].U10, [R12 Monthly Unique].U11, [R12 Monthly Unique].U12, [R12 Traffic].R1, [R12 Traffic].R2, [R12 Traffic].R3, [R12 Traffic].R4, [R12 Traffic].R5, [R12 Traffic].R6, [R12 Traffic].R7, [R12 Traffic].R8, [R12 Traffic].R9, [R12 Traffic].R10, [R12 Traffic].R11, [R12 Traffic].R12, [R12 Traffic].D1, [R12 Traffic].D2, [R12 Traffic].D3, [R12 Traffic].D4, [R12 Traffic].D5, [R12 Traffic].D6, [R12 Traffic].D7, [R12 Traffic].D8, [R12 Traffic].D9, [R12 Traffic].D10, [R12 Traffic].D11, [R12 Traffic].D12, Recipients.CountOfRpt_Code
HAVING ((([R12 Monthly Unique].Rpt_Code)=[Forms]![ReportCode]![RptCode]));

PARAMETERS [Forms]![ReportCode]![RptCode] Text ( 255 );
SELECT Chart.Rpt_Code, Chart.Usage
FROM Chart
WHERE (((Chart.Rpt_Code)=[Forms]![ReportCode]![RptCode]));

If the form is open, and the form name and textbox name are both correct,  I can't see any reason why you should be prompted for parameters.

I suggest you open the form, enter a value in rptcode and then do this...
Go to the vba code window (do Crl+G to get there in one step).

Then in the Immediate window type..

?Forms!ReportCode!RptCode
and see if you get the correct value shown.

The form wasn't open, I was hoping the report would open the form as a prompt, sounds like I need to open the form first, create a button that will open the report instead.