1. Prepare the mail merge to create a label but stop prior to completing the merge.

2. Press the Alt and F9 key. We will be entering control codes to force Word to accept the formatting layout in Excel. In the example Social Security Number is called SSN.

3. In the field name for Social Security Number, enter the following:
    {MERGEFIELD SSN\#000’-‘00’-‘0000 \*Mergeformat}

4. Press the Alt and F9 key to turn off the control code feature.

5. Complete the merge and your Social Security Number should look exactly like the formatting in Excel with the leading zeros and hyphens.