I don't need the work so I have no problem turning away business but I get to a point where the procrastinators frustrate me enough that I copy/paste a blurb telling them how to file an extension on IRS Direct Pay.  Even if you don't think you owe, pay them $1 and you get an extension on record, they'll refund it later.  If you think you owe, sent them more money.  There may be interest charges but if you want to avoid them in the future, contact me BEFORE the second week of April...