How calculations are built
Each calculator is built from the primary legislative source for that market — not from third-party aggregators or approximations. Rates, thresholds, bands and formulas are coded directly from the authoritative text, then cross-checked against official guidance and worked examples.
Where a calculation involves a professional judgment call (e.g. what portion of a property is land vs building for AfA purposes, or what constitutes "principal private residence") the calculator shows a reasonable default with a clear note that the user should verify for their situation.
All calculations are estimates. They do not constitute financial, tax or legal advice. Real-world outcomes depend on individual circumstances, local variations and professional judgment.
Key calculations used across markets
These are the fundamental formulas used across multiple calculators. Each market then applies local tax rates, thresholds and legislative nuances on top.
Primary sources by market
These are the authoritative documents each market's calculators are built from. Each inline methodology accordion within the calculator cites the specific article or section relevant to that calculation.
- HMRC SDLT guidance (post Oct 2024)
- Finance Act 2015 — Section 24
- PRA Supervisory Statement SS13/16 (ICR)
- Corporation Tax Act 2010
- HMRC Capital Gains Tax guidance
- Housing Act 2004 (HMO licensing)
- IRS Publication 946 (MACRS depreciation)
- IRC §168 (cost recovery)
- HUD/FHA guidelines (MIP, DTI limits)
- VA Lender Handbook (funding fee)
- CFPB mortgage disclosure rules
- State transfer tax schedules (all 50 states)
- Ustawa o PIT — art. 6 ust. 1a (ryczałt 8.5%/12.5%)
- Ustawa o podatku od czynności cywilnoprawnych (PCC)
- NBP — loan rate data (WIBOR)
- GUS — rental market indicators
- GrEStG (Grunderwerbsteuergesetz) — all 16 Länder
- §7 Abs.4 EStG (lineare AfA)
- §7 Abs.5a EStG (degressive AfA)
- §7b EStG (Sonder-AfA Neubau)
- GNotKG (Notargebühren)
- §656c BGB (Bestellerprinzip)
- CGI art. 150 U–150 VH (plus-value)
- CGI art. 32 (micro-foncier)
- D.Lgs. Loi de Finances 2025 n°2025-127 art.24
- BOFiP — LMNP réel documentation
- Barème IR 2026 (3 tranches post-réforme)
- DBG art. 33 (Schuldzinsenabzug, Säule 3a)
- StHG (Steuerharmonisierungsgesetz)
- Volksabstimmung 28.09.2025 (Eigenmietwert)
- OFAS — Säule 3a Limite 2026: CHF 7.258
- FINMA — Tragbarkeitsregeln (5% stress rate)
- TRLITPAJD RDLeg 1/1993 (ITP, AJD)
- Ley 5/2019 de Crédito Inmobiliario (AJD banco)
- AEAT — ITP rates all 19 CCAA (2026)
- RD 1426/1989 (aranceles notariales)
- RD 1427/1989 (aranceles registrales)
- Art. 3 D.Lgs. 23/2011 (cedolare secca)
- DPR 917/1986 TUIR (IRPEF, scaglioni 2026)
- Legge di Bilancio 2024 (affitti brevi 26%)
- D.Lgs. 23/2011 art.9 (IMU base imponibile)
- Agenzia delle Entrate Circolare 26/E/2011
When calculators are updated
Calculators are updated when the underlying legislation changes — not on a fixed publishing schedule. Each page displays a "Last reviewed" date. The triggers that prompt a review are:
Rate changes
Any change to a tax rate, band threshold or official levy — SDLT, GrESt, ITP rates, IRPEF scaglioni, Pilier 3a limits. Updated within days.
New legislation
Laws that alter the calculation structure — e.g. LF 2025 LMNP reintegration, UK Oct 2024 BTL surcharge, Italian Legge di Bilancio 2024.
Routine review
Each market is reviewed quarterly against official sources to catch minor changes, new guidance or court decisions that affect results.
What calculators do not cover
Being transparent about limitations is as important as being accurate about what is covered.
- Scotland and Wales (UK): UK calculators apply to England and Northern Ireland only. Scotland uses LBTT and Wales uses LTT — different structures with different rates.
- German municipal Grundsteuer: the DE Renditerechner uses an illustrative Grundsteuer figure. The actual amount depends on Bodenrichtwert and the local Hebesatz, which varies by Gemeinde.
- French SCI IS exit tax: the complex double-taxation on SCI IS exit (IS on accounting gain + PFU/IR on dividends) is modelled at standard rates. Actual liability depends on retained earnings history and individual tax position.
- Swiss cantonal tax rates: CH calculators use a composite Grenzsteuersatz input. Actual rates vary by canton, commune and family situation — Zurich ≠ Geneva ≠ Zug.
- Spanish CCAA variations: ITP reduced rates (young buyers, large families, disability) are listed but the eligibility conditions vary by CCAA and are not automatically applied.
- US state income taxes: the US Rental ROI calculator models federal tax (Schedule E) only. State income taxes on rental income are not included — they range from 0% (TX, FL) to 13.3% (CA).
- Inheritance and gift tax: no market's calculators model succession scenarios — a separate calculation type not yet built.
All 24 calculators with inline methodology
Every calculator below contains an expandable methodology section showing the exact formulas and sources for that specific tool.
| Market | Calculator | Key sources |
|---|---|---|
| 🇬🇧 UK | BTL Rental Yield | HMRC · PRA SS13/16 · Finance Act 2015 |
| 🇬🇧 UK | Stamp Duty (SDLT) | HMRC SDLT guidance · Oct 2024 rates |
| 🇬🇧 UK | Flip Profit | HMRC CGT · Finance Act 2015 |
| 🇬🇧 UK | HMO Yield | Housing Act 2004 · HMRC |
| 🇬🇧 UK | Section 24 / Ltd Co | Finance Act 2015 §24 · CTA 2010 |
| 🇬🇧 UK | Rent vs Buy | HMRC SDLT · Bank of England base rate |
| 🇺🇸 US | Mortgage Affordability | HUD/FHA guidelines · VA Handbook · CFPB |
| 🇺🇸 US | Rental Property ROI | IRS Pub. 946 · IRC §168 (MACRS) |
| 🇺🇸 US | Closing Costs | State transfer tax schedules · CFPB |
| 🇵🇱 PL | Kredyt vs Wynajem | Ustawa o PIT · NBP (WIBOR) |
| 🇵🇱 PL | Rentowność Najmu | Ustawa o PIT art. 6 ust. 1a (ryczałt) |
| 🇵🇱 PL | Pakiet Inwestora | Ustawa o PIT · GUS market prices 2026 |
| 🇩🇪 DE | Grunderwerbsteuer | GrEStG · GNotKG · §656c BGB |
| 🇩🇪 DE | Renditerechner | §7 EStG · §21 EStG · GrEStG |
| 🇩🇪 DE | AfA-Rechner | §7 Abs.4 · §7 Abs.5a · §7b EStG |
| 🇫🇷 FR | Rendement Locatif LMNP | CGI · LF 2025 n°2025-127 · BOFiP |
| 🇫🇷 FR | Plus-Value Immobilière | CGI art.150 U · LF 2025 art.24 |
| 🇨🇭 CH | Amortissement FR | DBG art.33 · OFAS · Votation 28.09.2025 |
| 🇨🇭 CH | Amortisation DE | DBG art.33 · StHG · BSV |
| 🇪🇸 ES | Calculadora ITP | TRLITPAJD · Ley 5/2019 · AEAT 2026 |
| 🇮🇹 IT | Cedolare Secca vs IRPEF | D.Lgs.23/2011 · TUIR · LdB 2024 |