On the Statement, the Description is a Formula.  Maybe look to modify the formula to print what you want on the Statement Form.  The check number shows on the inquiry screen to the left of the reference "DSCNT APPL", 

Here is the formula behind the Description on the statement.  If you do not want the check number referenced, you can modify the formula.

if {AR_StatementWrk.TransactionType} = "I" then
formula = {AR_StatementWrk.Comment}
elseif {AR_StatementWrk.TransactionType} in array ("C","D") and {AR_StatementWrk.PaymentReference} _
= "" then
formula = {AR_StatementWrk.Comment}
elseif {AR_StatementWrk.TransactionType} = "F" then
formula = "Finance Charge"
elseif {AR_StatementWrk.TransactionType} = "C" and {AR_StatementWrk.PaymentReference} <> "" then
formula = "Credit Memo: " + {AR_StatementWrk.PaymentReference}
elseif {AR_StatementWrk.TransactionType} = "D" and {AR_StatementWrk.PaymentReference} <> "" then
formula = "Debit Memo: " + {AR_StatementWrk.PaymentReference}
elseif {AR_StatementWrk.TransactionType} = "P" or ({AR_StatementWrk.TransactionType} = "X" and _
{AR_StatementWrk.InvoiceType} = "IN") then
formula = "Payment Ref: " + {AR_StatementWrk.PaymentReference} + {AR_StatementWrk.CheckNo} _
+ {AR_StatementWrk.PaymentType}
elseif {AR_StatementWrk.TransactionType} = "X" then
formula = "Ref: " + {AR_StatementWrk.CheckNo} + {AR_StatementWrk.PaymentType}
end if

Ah yes, I didn't even think to look at the statement form itself. Thanks for that!

I changed the `TransactionType` for "P" to this:

elseif {AR_StatementWrk.TransactionType} = "P" then
    If {AR_StatementWrk.PaymentReference} = "DSCNT APPL" THEN
        Formula = "PROMPT PAY DISCOUNT"
    Else
        formula = "Payment Ref: " + {AR_StatementWrk.PaymentReference} + {AR_StatementWrk.CheckNo} _
                    + {AR_StatementWrk.PaymentType}
    End If

Ah yes, I didn't even think to look at the statement form itself. Thanks for that!

I changed the `TransactionType` for "P" to this:

elseif {AR_StatementWrk.TransactionType} = "P" then
    If {AR_StatementWrk.PaymentReference} = "DSCNT APPL" THEN
        Formula = "PROMPT PAY DISCOUNT"
    Else
        formula = "Payment Ref: " + {AR_StatementWrk.PaymentReference} + {AR_StatementWrk.CheckNo} _
                    + {AR_StatementWrk.PaymentType}
    End If