I got married on 8/15. I went to my payroll and I change my status on my W4 to married 1. Now my husband in asking me if we can change it to him to married 1. but I don't want to get in ploblem at the end of the year. We make around 40,300 a year. What is the best thing to do.

Since it's November already, I'd leave it until the end of the year. After that, you can estimate your taxes for the next year and determine the number of deductions to take and the marital status.

I agree with Perito - wait and see whether too much, or too little, is being withheld now. You should also review the instructions for the W-4: there are specifics as to what to do if both husband and wife work. See: http://www.irs.gov/pub/irs-pdf/fw4.pdf From the instructions it appears that one or the other of you may have to claim just one credit, while the other may be OK with 2.