Accuracy of dividend adjustments & 10% deduction

[bullboy8]

Hi

For an index (say FTSE 100), how do you know the adjustment made by a provide like IG is correct? Is there transparency around this?

Also, if you are long, I believe IG returns 90% of the dividend? Since 16/17 tax year, the 10% notional pension credit was removed so why not payout 100%? Seems like they are profiting from this?

Thanks.