There would be two reasons this has follow up, as example: You have a qualifying project for under $5,000 and the 10% limit means you have a bit more headroom available on your next project that you submit to tax credit (this is my situation). The other would be, I suppose, the available and unused credit you have from the qualifying project, but didn't need to/get to use against taxable income. And now we have reached the end of my understanding of this tax regulation provision  🙂