To receive a voided check, you can download this right from your dashboard!
Click on your Account Icon (the first icon on the black Rho tool bar to the left) it looks like a house with a dollar sign:
Click on Cash (Checking) at the top in grey to reach your Checking Account.
Then click on Account Details to the right hand side of the screen.
From there you'll need to select the last option "Instructions to Receive Funds" and Voided Check will be there.