This was a one time distribution from a death benefit from my father. I believe it was an annuity that he had been receiving monthly checks from.
The question is:
I have no way of knowing for sure but I do believe he was getting monthly checks from this account. How do I answer (other than calling life insurance company please).
An annuity that was purchased by your father may have been purchased with "after tax" money. This means that he wasn't able to deduct the amount he used to purchase it, on his tax return. In this case then he may have a "tax cost basis" when the money is distributed. Some of the distribution would be taxable and some of it would be tax free. In general, the cost is the net investment in the contract as of the annuity starting date. The life insurance company should be able to provide you with this information.
You may want to contact the life insurance company to see if they can help. If this was not a Traditional IRA, then some of the money should be tax free.
If you are unable to find out if there is a cost basis then all of the distribution will be considered as taxable.