I haven't done my tax returns for at least 40 years. For most of my working life, I've paid estimated taxes, which were figured by my tax person, using the "safe harbor" provisions. I'm retired now, with SS and my wife has some part-time W-2 income, plus we have interest, dividends, and cap gains, which are greater than the combined SS and W-2 income. Our dividends and cap gains come as distributions from taxable Vanguard index funds. Anyway, I just found out today that the "safe harbor" provision only applies to folks with an AGI over $150K. We've always had much in excess of this amount, but now that I'm not working, we are getting very close to the $150K AGI level, possibly a little below or little above. Anyway, why does the IRS care about AGI when in comes to "safe harbor" estimated payments, or am I wrong about all of this. I would like to avoid having to do quarterly calculations.