You're missing a section on the bottom of your chart.

Who will pay for UBI? -- income tax. Raise the per capita income rate an average of £12,000, (£15,000 pounds minus the ~3,000 in savings you calculated earlier).

No net impact on the average taxpayer, little impact on the rich and massive impact on the poor.

I did the calculation for UK 2015-2016:

There are about 31 million taxpayers in the UK. The basic income tax rate of 20% for income up to £42k/year generates 33% of the income tax revenue. Let's agree that these are not the rich people we want to tax. (88,7% of Britons earn less than £50k/year.)

The higher (40%) and additional (45%) tax rates generate the rest 67% or £117 billion of the £174 billion income tax revenue.

In order to raise additional £472 billion, we would have to increase the higher and additional tax rates to approximately 211%.

As you can see, taxing the "rich" cannot raise enough money to give everyone unconditional poverty line minimum income.

Source: https://www.gov.uk/government/statistics/income-tax-liabilit..., https://www.gov.uk/income-tax-rates

"Let's agree that these are not the rich people we want to tax."

I definitely do not agree. BI is only viable if the average taxpayer sees no or very little net benefit from BI. So the average taxpayer would pay £15k extra in taxes if they receive £15k in BI. And £42k is above average (but not a lot, the medium income is £21k, but only a little more than half of adults are taxpayers)

The average taxpayer with income between £20k and £30k pays on average £2630 tax, some 10.7%. If you hand him over £15k and them tax him on average additional £15k then his tax rate must be around 44%. This will be extremely demotivational. A hard-working person will have barely more than absolute freeloader and if he tries to work extra hard you will take half of his reward.

No, he will have almost twice as much money as the freeloader.

More importantly, if both him & the freeloader are spending £15k on rent & food, then the freeloader has £0k of disposable income and the worker has infinitely more disposable income.

Another way of looking at it is that average taxpayer with UBI has an income of between £35k and £45k and has a marginal rate not much different from what people making £45k are paying right now. People making £45k aren't currently significantly demotivated by taxes, are they?

You are contradicting yourself.

"the average taxpayer would pay £15k extra in taxes if they receive £15k in BI"

vs

"Another way of looking at it is that average taxpayer with UBI has an income of between £35k and £45k".

Today a taxpayer with median income £21k takes home £19k net. After your reform, he will take home the same £19k net (remember: pay £15k extra in taxes if they receive £15k in BI). Except hew will now be way below the median and making only £4k more than the now ubiquitous dude Lebowski type.

The average taxpayer is well above £21k -- that's the median income, which includes the 40% not paying taxes and of course median is well below average due to tail effects.

25% of the working age population is economically inactive (with more being below the income tax floor) most of whom do not receive benefits (they're living off savings or others) even before you actively incentivise people not to look for work. It's going to cost a lot more than £12k per taxpayer, and with median UK household income being only £27k the taper for the working poor is going to be steep, and the middle classes seeing a net tax increase is going to include an awful lot of people struggling to pay off their mortgages.

And the thing is, many people who are actively looking for work or disabled already receive more than the UBI in other benefits being cut to fund this. The true beneficiaries? Upper middle class people who've paid off their mortgage, built up savings and wish to retire a decade or two earlier and traditional housewives. The losers? The working young and single people.

And, in the US, the administrative overhead is apparently less than about 10%, [1] which you're not actually going to completely eliminate unless you plan to cut pretty much all social support programs other than sticking money in a bank account every month.

[1] https://www.cbpp.org/research/romneys-charge-that-most-feder...