Yes – you are correct. The break-even point at which the current tax code and the proposed UBI tax code result in the same take-home income is £31,000 above which people would have slightly higher taxes. The mean full-time wage is significantly higher than what 50% of people earn (the median), largely due to very high earners pushing the mean up (incomes are pareto distributed).

Digging a little deeper though, looking at the Office for National Statistics website, it looks like the £35,000 figure is actually “Mean Household Disposable Income”, which is the income “after taxes and benefits” (the “Median Household Disposable Income” is given as around £30,000). Scaling these figures up to their pre-tax amounts gives £46,000 and £39,000 for mean and median respectively, but this is ignoring the “Household” in the name. It is unclear from the ONS what exactly the average household is, but according to https://www.statista.com/statistics/813380/average-number-of-adults-per-household-uk/ it is 1.9. This gives a mean gross income per adult of £24,200 and a median gross income per adult of £20,500. Of course, while we have factored out the tax, we have not been able to factor out the benefits, so these are both inclusive of benefits in some way, and therefore will still be overstated to some degree.

Taking a median from the income tax liabilities table from my previous comment gets you to £15,000 (half of the adult population of 54.2m is 27.1m. 23.2m people earn less than £11,850 and 4.1m people earn more than this but less than £15,000. This comes to 27.3m, so the median person probably earns around £15,000).

This can be compared with the UK GDP per capita of $42,950 = £32,200. This is a mean, so will be higher than the median earnings, but it is not a measure of individuals incomes – it is measuring the broader domestic economy, so will be skewed upwards by domestic companies paying salaries to non-residents and dividends to international shareholders.

Going back to the idea of households, it can be stated that households with 2 earners would have to be earning a combined gross household income of greater than £61,000 (2 x £31,000) before they saw higher taxes.

All of this is further complicated by the fact that some of the people with low or zero incomes will actually be “stay-at-home” partners of wage-earners, therefore their combined “household income” may in fact still increase on net. Households in this situation are effectively almost guaranteed to see a tax cut due to the measly nature of the “Married Couple’s Tax Allowance” which only allows you to transfer £1,250 of your personal allowance to your spouse. Under the UBI tax proposal, a couple where one person has income and the other has zero income would still receive UBI for both people. A £16,000 UBI coupled with a 47% flat tax rate is actually a tax cut for absolutely everyone (albeit a very tiny one for millionaires… Also most millionaires are good at avoiding taxes, so most will find a clever way for their spouses to utilise their personal allowance, therefore making this no longer apply).