One problem with the IRR method is that:
it does not take account of cash flows over a project’s full life.
it does not take account of the cash outflows.
it does not provide a rate of return.
it values a dollar received today the same as a dollar that will not be received until sometime in the future.
it assumes that the cash flows generated by a project can be reinvested back into the same project, and this assumption is often not valid.