Altering a return

I had my preparer at HR block file my return and I got a notice from the IRS saying they needed more info. I called IRS and apparently my preparer forgot to fill out a line. Can I just print out a copy of the return, write in pen what I need and send it back. Or am I going to have to take it back to HR and have them change it. Because if I have to take it back I feel like they'll charge me an outrageous fee.