Your code is doing an implicit conversion somewhere. The obvious places are the string concatenation with + . If any of the arguments is a number, then + is interpreted as numeric addition -- and you get an error.

Less obvious places are other operations, such as JOIN conditions. If one column is a string and the other a number, then SQL Server attempts to convert the string to a number -- and you can get an error.

So, I would try the following.

Replace:

(B.Description + '-' + B.Product_Code + '(' + D.Brand_Name+ ')') AS Description,

with:

(B.Description + '-' + CAST(B.Product_Code as VARCHAR(255)) + '(' + D.Brand_Name+ ')') AS Description,

This is only necessary if Product_Code is a number.

A.DOID LIKE '%' + @DOID + '%'

with:

CAST(A.DOID as VARCHAR(255)) LIKE '%' + @DOID + '%'

This is only necessary of A.DOID is a number.

Change the type of @brcode to a string. This is only necessary if a_BR_CODE is a number.

If these do not work, you will have to look at the JOIN conditions to see if any of them mix types.

I also think that we need to know the data types of the DOID fields in the various table. My guess is that there is a data type mismatch on one of the joins.

try the following:

CREATE PROCEDURE [dbo].[wsp_Display_Invoice]
     @DOID NVARCHAR(50),
     @brcode INT
AS
BEGIN
    SELECT DISTINCT 
        A.Item_Code,
        (B.Description + '-' + B.Product_Code + '(' + D.Brand_Name+ ')') AS Description,
        A.Quantity, B.UOM, A.Rate, A.DOID,
        C.Doc_No, B.Tax_Percentage AS Tax, B.Tax_Percentage AS Tax1,
        F.QuotationID
    FROM 
        DO_T A 
    INNER JOIN 
        inv_Item_Master B ON A.Item_Code = B.Item_Code 
    INNER JOIN 
        DO C ON A.DOID = C.DOID 
    INNER JOIN 
        Inv_Brand D ON D.Brand_ID = B.Brand_ID 
    INNER JOIN 
        Quotation_T F ON F.DOID = A.DOID 
    WHERE 
        CONVERT(varchar(50), A.DOID) LIKE '%' + @DOID + '%' 
        AND a.BR_Code = @brcode
END