How to negotiate a high salary after receiving a job offer?

I believe I am about to receive a job offer. I was asked to fill out an employment application during the interview process but before I had a lot of information about the position. I have since been through three interviews and have a better understanding of the position and it seems a lot more complicated and demanding than I initially thought. I now realize that the desired salary I put on the form is too low. Would it be frowned upon to try to negotiate a higher salary once I receive the offer and say that now that I understand more about the position, I believe the pay should be higher? Not sure how to go about this. It's a very large company.