If you are filing jointly with your new wife, but your ex-wife has a right to see your actual tax information, then she will be able to see you new wife's information, too--they are part of the same return. If you cannot negotiate some alternative to provinding the tax return (providing your personal W-2 and/or 1099s--they should have the most relevant information for your ex wife?), you may want to consider filing separately from your new wife, if you or she feel strongly about showing her financial to the ex wife.
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