Question: They are asking for the 1040 income tax return form but my parents were not able to file taxes this year so what is an acceptable substitute?
Thanks
Answer: I guess I wonder why they were "not able to file taxes this year." If they had income, they have to file an income tax return whether they think they owe taxes or not. But aside from that:
You could provide a written statement explaining why your parents did not file taxes and then provide pay stubs or copies of bank statements instead. The reason they want a tax return is that it is difficult to fake info on a tax return, whereas if you provide a bank statement it might just be one of several bank accounts you have
You could provide a copy of last year's tax return.
You could provide copies of your parents' W-2 forms for 2008.
Others: