Eligibility for tax free childcare and 30 hours free childcare

Hi, I want to understand more about the 'earning £100k+' eligibility. I've already called your helpline but I believe the information they've given me is incorrect. Is your eligibility for both of those benefits checked against your taxable income or your adjusted net income, as I've seen both referred to in your guidance? [The helpline told me it's against your income after tax, which as I say I'm pretty sure is incorrect.] Are there any documents you can look at to easily find the earning figure which you're interested in to assess eligibility? For example, the total pay figure on your P60? I also want to check my understanding with two examples please. 1: If you earn gross salary £100k and receive a £10k bonus, but do bonus sacrifice to put that £10k straight into your workplace pension, would you then only be seen to earn £100k for this eligibility and therefore be eligible? 2: If you earn gross salary £100k but then get a pay rise to £120k , but do salary sacrifice and put £20k straight into your workplace pension, would you then only be seen to earn £100k for this eligibility and therefore be eligible? Thank you

Hi Sarah,
Please see details on adjusted net income here:
Personal Allowances: adjusted net income
The Salary sacrifice already reduces your taxable income so would not be deducted again. 
Thank you.