Guides · Reconciliation
Why the calculator shows a different number than your tax software
What the calculator is
The TaxToNet calculator is a deterministic, single-filer baseline. It applies:
- The current year's federal brackets (US) or personal allowance + bands (UK E/W/NI).
- Employee-side social contributions: Social Security + Medicare (US); Class 1 employee NI (UK).
- The standard deduction (US) or Personal Allowance (UK).
- No credits, no pre-tax deductions beyond the standard allowance, no state tax, no phase-outs, no Married/HOH variants.
The output is the take-home pay for a hypothetical single employee at the same gross, in the same jurisdiction, with no elections. It is the reference point.
What software adds on top
Tax software applies the same brackets but layers:
- Your actual filing status (US: single, married filing jointly, head of household; UK: marital status for tax code purposes).
- Your dependents (US Child Tax Credit, UK Child Benefit — separate from tax).
- Pre-tax elections: 401(k), HSA, FSA, salary-sacrifice pension.
- Itemized deductions (US Schedule A).
- Credits: education, retirement-savings, EITC, child care, energy credits, etc.
- State and local tax (US: each state has its own calculator).
- Investment income, capital gains, rental, self-employment (filed separately or stacked into the same return).
- Phase-outs and tapers (US: IRA deduction phase-out, CTC phase-out; UK: Personal Allowance taper).
Some of these reduce taxable income, some reduce the tax bill directly, some reduce the refund you would have received (withholding gap). The software applies all of them in order; the calculator applies none of them.
Reconciling US numbers
A US single filer earning $80,000 in 2026, no dependents, no 401(k), standard deduction only — the calculator output is:
| Line | Calculator |
|---|---|
| Gross | $80,000 |
| Standard deduction | $16,100 |
| Taxable | $63,900 |
| Federal income tax | $8,727 |
| Social Security | $4,960 |
| Medicare | $1,160 |
| Take-home | $65,153 |
Now add the things software includes:
| Adjustment | Effect | Tax software output |
|---|---|---|
| Baseline (above) | — | $8,727 federal tax |
| 5% to 401(k) ($4,000) | Reduces taxable pay to $59,900 | $7,727 (-$1,000) |
| HSA contribution ($4,400) | Further reduces taxable pay to $55,500 | $6,847 (-$880) |
| Saver's Credit ($1,000) | Direct credit against tax bill | $5,847 (-$1,000) |
| Child Tax Credit (2 kids, $4,000) | Direct credit | $1,847 (-$4,000) |
| State income tax (5%) | State-level bill on top | +$3,100 (added) |
| Final tax bill | $4,947 |
The calculator says $8,727. The software says $4,947 federal + $3,100 state. The difference is the $4,000 401(k) + $4,400 HSA + $1,000 Saver's Credit + $4,000 CTC, minus the state tax piece. Same brackets, very different outcome. The calculator is the "before credits and deductions" baseline.
Reconciling UK numbers
A UK single filer earning £60,000 in 2026/27, no salary sacrifice, no pension contributions — calculator output:
| Line | Calculator |
|---|---|
| Gross | £60,000 |
| Personal Allowance | £12,570 |
| Taxable | £47,430 |
| Income tax (basic rate × 80% of taxable) | £7,486 |
| Employee NI (8% on £37,430 + 2% on £9,730) | £3,189 |
| Take-home | £49,325 |
Adding the things HMRC Self Assessment might include:
- Salary-sacrifice pension (£3,000 of the £60,000). Reduces taxable pay and NI base. Tax saving ~£600 income tax + ~£240 employee NI = ~£840.
- Personal Allowance taper at £100,000+ (this earner is below it, so no change).
- Marriage Allowance transfer if their spouse is a basic-rate non-earner: £1,260 transferred, saving £252.
- Dividend allowance (£500) and dividend income above that — taxed separately on SA108.
- Self-employment profits (Schedule SA, with Class 2 + Class 4 NI).
For a vanilla PAYE employee with no other income, the calculator's £7,486 income tax and £3,189 NI match what HMRC should collect on a £60,000 salary. The reconciliation collapses to "if you have no other sources, the calculator is right."
When the gap is real
Three cases where the calculator and software diverge by more than round-off:
- Pre-tax elections you forgot about. 401(k), HSA, FSA, salary-sacrifice pension. The calculator assumes zero. If you have any of these, your actual tax bill is lower than the calculator says.
- Credits you qualify for. CTC, EITC, Saver's Credit, education credits, retirement contributions credit (US); Marriage Allowance transfer, gift-aid, charity donations (UK). Each can be worth $1,000-$5,000+ of tax saving.
- Income from a source the calculator doesn't see. Capital gains, dividends, rental income, self-employment. These don't change the federal/PAYE income tax on the salary, but they add a separate tax bill that the calculator does not model.
If you find a gap that doesn't fit one of those buckets — same filing status, same dependents, no extra deductions, no other income — that's a calculator bug. Report it via the corrections page with the specific numbers; the team will trace the discrepancy.
How to read both
Use the calculator as the reference baseline — the number that a hypothetical no-credits, no-deductions filer at the same gross in the same jurisdiction would owe. Use your tax software as the real number for your specific situation. The difference between the two is the value of the credits and deductions you applied.
If the difference is large, your credits and deductions are doing significant work — that's a feature, not a bug. If the difference is small (under $500 / £300), you're close to the baseline scenario the calculator models, which is a useful reality check.
The calculator is not a substitute for tax software. It is a way to understand the brackets and contributions in isolation, without your specific situation layered on top. Use it to learn how the math works; use the software to file the return.