Congress itself is considering a bill, the Children's Gun Violence Prevention Act, which would hold gun-owners responsible for keeping guns locked away from children and would require gun manufacturers to make child-proof weapons.

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All over the rich world, there are parents who leave the child-proof lids off medicines because they find them so fiddly, and office workers so irritated by self-closing fire doors that they prop them open.

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As a result, "there's a tremendous amount of discretion, but that discretion is really limited to the proof of the child's actual lifestyle needs, " he said.

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Ms. Coultman lost on the child care credit because she had no proof of her expenditures not even remembering how much they were.

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For instance, the IRS currently can't deny a tax credit for adopting a child to someone who has not provided adequate proof of the adoption, according to Russell George, Treasury Inspector General for Tax Administration.

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Indeed, birth certificates showing a child was born on U.S. soil are now proof of citizenship.

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