In 2008 my wife's mother passed and left her an inheritance of 50k and we purchased a home in Idaho. Idaho does not have a inhertance tax. We filed in Idaho last year. My question is how much if any does my wife have to pay the IRS?

Nothing. Inheritance taxes are paid by the estate not the heir. Besides there is a threshold of $2 million.

Some one must file your wife mother's last tax return and all previous tax return if the income was more than the filing requirement.

Your wife does not have to pay any tax on inheritance. However, she will still be responsible for paying her mother's tax dues, if any.

Some one must file your wife mother's last tax return and all previous tax return if the income was more than the filing requirement.

Your wife does not have to pay any tax on inheritance. However, she will still be responsible for paying her mother's tax dues, if any.

Not right - the executor of the estate (sometimes called the "personal representative") is responsible for filing the deceased's final tax return and paying anything owed the IRS (or other creditors) out of the mother's estate assets. The daughter is NOT responsible for filing the estate's taxes unless she is the executor ("executrix" if you are old school), and is absolutely not responsible for paying any taxes due.