"The lower National Insurance paid by the self-employed is forecast to cost our public finances over £5 billion this year alone"?
Some might have though he was implying that if only the self-employed paid what employed people pay then the Exchequer would be £5bn a year to the good.
But it's not quite like that.
Yes, Mr Hammond is simply totting up what he would get if all the self-employed were employed - and subtracting what he receives from them at the moment.
He reckons he would be £5.1bn a year better off.
Yet most of that large sum would come from the National Insurance paid by employers, the so-called tax on jobs.
Employer NICs are a substantial 13.8% of pay.
That's not money deducted from wage packets, even if employers see it as part of the cost of taking on staff.
The self-employed do contribute less, £2.80 a week and 9% of pay over £8,060, compared with the straight 12% contributed by employees.
But not £5bn less.
In fact some would argue that they are pushed into self-employment by companies who want to avoid having to pay employer NICs.
Even so, it was individuals whom the Chancellor targeted in his short-lived National Insurance hike, not companies trying to trim their tax bills.