Purnsley company paid estimated tax payments of $40,000 in 2020. on april 11, 2021, it filed its 2020 tax return showing a $150,000 tax liability. thus, purnsley company paid the $110,000 balance at that time. on june 2, 2021, purnsley company filed an amended return for 2020 because of an error discovered; the amended return reveals a reduced tax liability of $60,000. which internal revenue codes, regulations, or court cases apply to this case? i could really use your help with this tax memo.