“This is the spreadsheet bit”, said Philip Hammond in the opening section of his first spring Budget on Wednesday. He was playing to the galleries by acknowledging his reputation for being a bit of a boring accountant; but as any boring accountant knows, the spreadsheets only tell you half the story.

He made decent theatre of his aim of creating a fairer, more level tax regime across those in employment and the self-employed. Unfortunately for the Chancellor, someone was paying attention to the Conservative manifesto during the 2015 election campaign. Woops.

So Thursday’s headlines were dominated by howls of protest, derision and perhaps even a little schadenfreude that Mr Hammond had apparently reneged on the manifesto pledge not to increase National Insurance.

Ah, said the Chancellor at first, but we meant Class Two NI; what we’re proposing is to change is Class Four NI. Predictably, very few people replied: Oh, well, if you’d said that...

By Friday, the Prime Minister was forced to clarify that, actually, the Commons wouldn’t be asked to vote on the changes until autumn, and pending a review into benefits for the self-employed.

In case you missed it, self-employed earnings between £8,060 and £43,000 are currently taxed at nine per cent. Under the plans brought forward in the Budget, that earnings band will be subject to an extra one per cent of tax, bringing it to 10 per cent from next year; increasing to 11 per cent the year after. And in case you need reminding, there’s already an additional two percent surcharge on profits above £43,000.

Like I said – the real interest in this lies behind the numbers; the ‘so what?’ factor. Partners in professional services firms, such as lawyers (OK, yes, and accountants), will be affected – but they tend to be higher earners, aren’t likely to attract much sympathy and will be better able to absorb the additional tax burden. Those with the broadest shoulders, etc.

At the other end of the scale, self-employed tradespeople, for example, the impact is likely to be felt more keenly. That’s where it might get interesting. For smaller self-employed traders, there may come a time where it makes sense for them to make the leap into becoming a limited company, with corporation tax on its way down over the next couple of years.

The downside? Additional administration, financial reporting requirements and so on. There’s also the new measure whereby the threshold for tax relief on dividend payments to director shareholders has been reduced from £5,000 to £2,000. On the positive side, liability burden is limited to the business if something goes wrong – and there’s the possibility that corporate tax is a (relatively) more stable picture than income tax.

On that note, there’s an interesting conflict here – if another was needed – between the Holyrood and Westminster tax regimes. Self-employed traders pay income tax on their earnings, which is devolved to the Scottish Government; if more of them convert their businesses to limited liability companies, their business earnings will be taxed as such and collected by the UK government. Of course, I’m sure this hasn’t entered the heads of anyone in Downing Street.

One measure which brings an element of relief to smaller businesses is the deferral of the Making Tax Digital regime, whereby – as the name suggests – tax administration for all unincorporated businesses and companies will move fully online. Unusually, the self-employed and unincorporated businesses will have to implement this first, before incorporated. The Chancellor has given the smallest businesses an extra year to get ready, which is helpful, rather than staggering.

But nothing about this Budget was staggering. The measures introduced couldn’t be described as much more than some broad tinkering, and some of the more significant points raised – such as the review of North Sea taxation – were shrouded in opaque promises of ‘discussion papers in due course’ and similarly vague language.

Still, Spreadsheet Phil made a resounding success of at least one element of his inaugural and final Budget. After his knowing gag about his own nickname, he asked the deputy speaker to bear with him on ‘the spreadsheet bit’ because he had a reputation to uphold.

On that front – job done.

Ricky Murray is a tax partner in business advisory firm Johnston Carmichael’s Glasgow office.