If you are certain of that, thanks for the input.
Its a bit tricky but its possible. Its one of the reasons the IRS is willing to even do an offer-in-compromise. For the tax debt to be dishargeable in bankruptcy the debt has to be assessed for at least three years. If the collection proceedings are tolled, like when an offer is made or by prior bankruptcy the the period the IRS has to collect is extended.
The assessment date is not exactly when the return is filed, its when the IRS gets around to recording it.
One of the problems with the TP'er route is that the three years never begins until they file. Anyone who owes and cannot pay is much better off filing as early as possible so that the statute of limitations starts running.
The other little known collection fact is the IRS can only chase you for ten years (unless they get a judgement) which they normally don't do. Again the ten years doesn't start until the tax is assessed.