Found a fix, I moved the Append , and replace section under the declairations and added
SELECT Payreceived before the SUM line.
Thanks for the help.

>>When running the code below the amount returned for paytest is double the amount just entered into the pytendered and not the actual total. But when I run the SUM command as is in the Command Window and ?print the result it is fine.
>>
>>Public NQUAN,NNOW,LWAIT,CRAMOUNT,CTHIS,paytest,NTICK
>>paytest=0
>>LWAIT=.T.
>>CTHIS=This.Value
>>NTICK=INVOICE.NTICKET
>>SET CONSOLE OFF
>>Sum PAYRECEIVED.namount For PAYRECEIVED.NTICKET = NTICK To CRPAY
>>CRAMOUNT=INVOICE.YTOTALSALE-CRPAY
>>Do Case
>>
>>Case CTHIS="RENTAL"
>> Thisform.COMMAND2.Click
>> LWAIT=.T.
>>
>>Case CTHIS="CANCEL"
>> LWAIT=.T.
>> Delete All For SALES.NTICKET = Val(Sys(3004)) In SALES
>> Delete All For INVOICE.NTICKET = Val(Sys(3004)) In INVOICE
>>
>>Case CTHIS ="CASH"
>> LWAIT=.T.
>> Append Blank In PAYRECEIVED
>> Replace PAYRECEIVED.namount With PYTENDERED In PAYRECEIVED
>> Replace PAYRECEIVED.NTICKET With NTICK In PAYRECEIVED
>> Replace PAYRECEIVED.ctype With "CASH" In PAYRECEIVED
>> SUM payreceived.namount FOR payreceived.nticket = ntick TO paytest
>> Do Case
>> Case paytest < INVOICE.YTOTALSALE
>> This.Parent.Tendered.SetFocus
>> Case paytest >= INVOICE.YTOTALSALE
>> This.Parent.COMPLETESALE
>> LWAIT=.F.
>> Endcase