IF OBJECT_ID(N'dbo.STITransaction', N'U') IS NOT NULL
BEGIN
    IF NOT EXISTS
    (
        SELECT 1
        FROM sys.columns
        WHERE name = N'TaxId'
              AND object_id = OBJECT_ID(N'dbo.STITransaction')
    )
    BEGIN
        ALTER TABLE dbo.STITransaction ADD [TaxId] VARCHAR(MAX);
    END;

    IF NOT EXISTS
    (
        SELECT 1
        FROM sys.columns
        WHERE name = N'InvoiceNo'
              AND object_id = OBJECT_ID(N'dbo.STITransaction')
    )
    BEGIN
        ALTER TABLE dbo.STITransaction ADD [InvoiceNo] VARCHAR(MAX);
    END;

END;