Clarification: the child needs "earned income". Dividends, interest, capital gains or gifts do not count.
I concur with Barry. At age 4, there is little that a child can do to earn money. Model or child actor is about it. You often see the children of entreprenuers in their TV ads (Buy a car from my dad!) and is reasonable for the child to be paid for participating. This means the child could have W2s and would be filing a tax return (the paperwork that Pax is probably refering to). This is one of the benefits a small business has over a payroll worker.
Teens are much more likely to have earned income. This can include a newspaper route, babysitting, dog watching, yard work, and my favorite selling lemonade on a hot day. You can make a more convincing case of hiring them for a small business. From age 15 on, my kids have been paid for filing, copying, shredding and cleaning to give them a small income to qualify for Roths. The Roth contribution does not have to come from the kid's account, but they must qualify based upon their own earned income.
You may want to consider other kinds of savings or investments for a 4 year old child. You could be the custodian for a tax managed or index mutual fund. You could buy stocks and hold them for a long term (to avoid tax events. Some colleges/states have prepaid tuition plans. There is a range of "529 Plans" and also the Coverdale Plans (also called Education IRAs). Some of these are flexible and good, some are just awful. Here are some website references on minor investing.
http://www.nasd.com/Investor/Choices/Colle.../529_saving.asp http://www.kiplinger.com/tools/managing/co...1/states01.htmlhttp://www.ici.org/ici_frameset.htmlYou will also find Fidelity, Vanguard, Twentieth Century, Scwab and a host of other mutual fund families and brokerage have their own plans.
Some key things to consider: how flexible are these plans, will the plan maximums meet the anticipated goals, when (if) the child gets control of the funds, what are allowed expenditures, what investment options are offered, fees, can they be shared across family members or are they child specific, and what happens if the child does not go to college.