About TaxWedge

Every UK salary calculator will tell you your take-home pay. Almost none will tell you what your next £100 is taxed at, and that is the number behind every decision anyone is actually making: whether to take the rise, what the bonus is worth, whether to put it in the pension, what the promotion past £100,000 really pays.

TaxWedge computes both, plus the part your payslip never shows — the employer National Insurance paid on top of your salary. The gap between what an employer spends and what reaches your account is called the tax wedge, which is where the name comes from and what the site is organised around.

There is no byline, deliberately

Search guidance rewards content with a named author and stated expertise, and inventing one would be an easy way to look more credible. It would also be a lie about who checked the arithmetic, on a site whose only asset is that its arithmetic is checkable. So instead: the method is written out in full, every rate is listed on sources with the date it was read, the calculation is the same code you can run in the calculator, and there is an address for corrections. If a real author with real credentials is added later, they will be named here.

This is not advice

It is arithmetic on published rates. It does not know your tax code, your benefits, your other income or your circumstances, and it does not recommend anything. For a decision that matters, check HMRC's estimator or speak to someone qualified.

Contact

Corrections: corrections@taxwedge.com
Anything else: hello@taxwedge.com

What the site actually claims to know

TaxWedge knows one thing well and says so loudly: how the published UK income tax, National Insurance and student loan parameters combine, for one employment taxed through PAYE on a standard code. Inside that boundary it is unusually precise — the band boundaries are not typed in, they are discovered by running the engine across the income range and bisecting to the nearest pound, and the build fails if the boundaries it finds do not reproduce the statutory ones. Outside that boundary it knows nothing, and every page that makes a calculation lists the assumptions it made to get there.

That combination — narrow scope, verifiable inside it — is the whole editorial position. A calculator that quietly guesses at benefits in kind, a non-standard tax code or a second job would be more useful if it were right and actively harmful if it were not, and there would be no way for a reader to tell which. Refusing the question is the honest answer.

Why the marginal rate is the organising idea

Almost every take-home calculator answers "what have I got". Almost none answers "what is the next pound worth", and the second question is the one behind every decision a person is actually making: whether to take the rise, what the bonus lands as, whether the pension contribution is worth it, what the promotion past £100,000 really pays. Those all turn on the rate at the margin, which in the UK is routinely twenty points away from the effective rate and, in two well-known stretches, higher than any rate in the statutory table.

The system produces those stretches without ever legislating them. The personal allowance taper above £100,000 withdraws tax-free pay at £1 for every £2 earned, which taxes the same pound twice and creates a 60% band that appears in no rate table. Add a student loan and it is over 70%. In Scotland the bands and the National Insurance thresholds cross rather than line up, which opens a window where the rate on further pay is higher than it is £20,000 further up the scale. Those are emergent facts about how the pieces interact, and the only way to show them honestly is to compute the whole curve and publish it.

Who is behind it, and why there is no byline

Search guidance rewards a named author with stated credentials, and inventing one would be an easy way to look more authoritative than this site has earned. It would also be a lie about who checked the arithmetic, on a site whose only real asset is that its arithmetic can be checked by anyone who wants to. So there is no byline and no invented panel of experts.

What is offered instead is the thing a byline is supposed to be a proxy for. The method is written out in full, including the parts that are approximations and why. Every parameter is listed on sources with the government page it came from and the date it was read. Every correction is published at changes, including the ones found before launch, because a log that only starts once the site is popular is not a log. And the arithmetic is shown on the page rather than asserted, so a reader with a payslip and ten minutes can audit any figure here without trusting anybody.

What it is deliberately not

It is not tax advice, and the difference is not a formality: advice is given by someone who knows your circumstances and takes responsibility for the conclusion, and neither applies here. It is not a benefits calculator, and it does not attempt Universal Credit tapers, council tax support, or the interaction between them and earnings — that interaction produces marginal rates far above anything on this site, and modelling it properly needs household circumstances a salary box cannot ask for. It is not a self-assessment tool. It does not store, transmit or remember anything you type.

How it is built

Every page is generated in advance from a single tax engine and written to a file; there is no application server and no database. The same engine file is sent to your browser unchanged, so the calculator and the pre-built pages cannot disagree — a test asserts they are byte-identical, because two copies of a tax rule is one copy too many. The parameters live in one data file with a source URL and a retrieval date attached to each. Roughly twenty thousand assertions run against the built site on every change, and a page that falls below the site's own thresholds for depth, uniqueness or internal linking fails the build.

Corrections

If a figure here disagrees with your payslip, the usual explanations in order are a non-standard tax code, a benefit in kind, a workplace pension deducted before tax, or National Insurance charged on a pay period containing a bonus — National Insurance is worked out per period rather than annually, which is why a bonus month can take more than the annual figures suggest. If none of those fits, it may simply be wrong here, and that is worth an email to corrections@taxwedge.com. Corrections are published with a date whether or not anyone would have noticed.

How to tell whether to believe a calculator

Three questions separate a calculator worth trusting from one that merely looks confident, and they work on any site including this one. Does it state the tax year on the page with the figure? Does it show the arithmetic, band by band, or only a total? And does it say what it does not model? A tool that answers all three is making claims you can check. One that answers none is asking for faith.

Where the name comes from

The "tax wedge" is the OECD's term for the gap between what an employer spends on a job and what the worker receives. It is the measure used to compare countries precisely because it cannot be gamed by moving a tax from one side of the payslip to the other. Organising a UK calculator around it is unusual, and it is the whole point: the employer's National Insurance is real money spent on employing you, and leaving it out makes the burden on a job look about a third smaller than it is.