I have a death benefit that was payable to a trust. I'm doing a 1099 for the trust to show the amount received. Do I show on the 1099R box 2a that the entire amount is taxable?

I have a death benefit that was payable to a trust.
Do you mean paid, not payable?

I'm doing a 1099 for the trust to show the amount received.
Are you doing the 1099 on behalf of the payor trust to show the amount paid or the recipient trust to show the amount received?

Do I show on the 1099R box 2a that the entire amount is taxable?
Was the death benefit (i) an account balance or (ii) death proceeds of life insurance?