Bob, technically the taxpayer has defaulted by incurring a new penalty. However, my experience with this is that I have the client slightly overpay so that they end up with a small refund. I find that the IRS will not default the agreement. I am unsure if this is just pragmatism on the part of the IRS or a glitch in their system, and I do not want to bring it to their attention (and have them fix the glitch).
