The way it works is that you document your income to the satisfaction of an escribano (something like a notary), who then writes a letter for Immigration. There are various ways of documenting your income, and different escribanos have different requirements. Then Immigration may or may not accept the escribano's letter, so it helps to choose an escribano who is experienced with writing letters for this purpose so you don't have to keep going back and forth until they get it right.Â
I haven't heard of anyone using a tax form to demonstrate their income, but I suppose it might be possible.Â
The best thing is to start working with an attorney or an immigration consultant, who can answer your questions and give you guidance according to your particular situation.Â
Shirley