The bill includes powers to allow for the introduction of an earnings taper, so that ESA and JSA (there will be no Contribution Based or Income Based any more as IB JSA & ESA are abolished) will be reduced at a constant rate as earnings increase in the same way as universal credit. This rate will be prescribed in regulations.
This shouldn’t affect the incomes of anyone whose income is topped up by Universal Credit, as a penny drop in one means a penny drop in the other, but it will, again, affect those who, for example, have partners in work. That’s assuming that it will be couples earnings that are taken into account. If it affects only the individual then it might have been simpler to add the benefits onto the relevant earnings.
Once more, it will be the regulations that will give us the real intention and effect of the power.