Reduction of gene flow. However, speciation might also happen in a population with no specific extrinsic barrier to gene flow. Imagine a situation in which a population extends over a broad geographic range, and mating throughout the population is not random.
The Internal Revenue Service places restrictions on how far back you can amend your tax return, regardless of whether you owed tax or received a refund. Filers must use Form 1040X to amend a return and should only file an amendment to report certain changes. You have three years from the due date of the original return or two years from when you paid tax owing to submit an amended return. A pen next to an income tax form.
You must file a federal income tax return for any tax year in which your gross income is equal to or greater than the personal exemption amount and standard deduction combined (per the Form 1040 Instructions for the corresponding tax year). Generally, you need to file returns going back six years. Copy: You can request a copy of your tax return, but in most cases you must pay a fee to do so (currently $50). 2  Use Form 4506, Request for Copy of Tax Return (PDF), to request a copy of your tax return. 3  Copies of Forms 1040, 1040A, and 1040EZ are generally available for 7 years from the date you filed the return.