Primary formula
For an owner-occupied main residence, the estimated annual charge is:
Entered property value × 0.0048.
For a second home, empty home or non-resident-owned home, the estimated annual charge is:
Entered property value × 0.0096.
Results are rounded for display to the nearest pound. The underlying calculation uses the full decimal value.
Fairer Share's evidence describes annual valuations with the taxable figure based on the average value over the preceding three years. The user can enter their own reasonable estimate of that average or use the optional sold-price tool's three-year proxy. Neither is an official taxable valuation.
Sold-price home estimate
The optional estimator is for people who do not know their property value. It retrieves completed sales for the supplied full postcode from HM Land Registry Price Paid Data. Only standard-price transactions, known as Category A, are used. “Other” property types, additional-price-paid transactions, deleted records and implausible values are excluded.
For each address, only its latest eligible sale is retained. The sale price is then moved to the latest available month using the matching property-type series in the UK House Price Index:
Adjusted sale price = sale price × latest HPI ÷ HPI in the sale month.
Sales without a matching index month and sales more than 15 years old are not used. Comparable sales are normally restricted to the chosen dwelling type. If the user chooses “not sure”, more postcode-level evidence is required unless a likely prior sale supplies the registered property type.
The central estimate is a time-weighted median of the adjusted comparable prices. A sale's weight halves every 36 months. When there are at least eight comparables, conventional interquartile-range filtering removes extreme outliers if enough evidence remains. If an optional house or flat number appears to match a prior sale, its HPI-adjusted price is blended with the comparable median, with less influence as that sale gets older.
At least three same-type sales are required. Where a possible prior sale for the supplied property is found, at least two other comparables are still required. Without a property type inferred from a prior sale, “not sure” requires at least five sales. If the threshold is not met, the tool returns no estimate rather than substituting a regional or national average.
The displayed range is based on the weighted 20th and 80th percentiles, widened to a minimum margin according to the evidence confidence. The confidence label considers sample size, recency, price spread, whether the dwelling type is known and whether a likely prior sale was found. It describes the available data, not guaranteed valuation accuracy.
To create the optional three-year-average proxy used by the tax calculator, the current estimate and range are multiplied by the average of the preceding 36 monthly HPI levels divided by the latest HPI level. This is a historic index proxy, not a forecast or an implementation of any future statutory valuation rules.
Price Paid Data does not include floor area, bedrooms, condition, extensions, plot size, views or lease details. The estimate is therefore an indicative postcode-level comparable-sales guide, not a survey, RICS valuation, lender valuation, estate-agent appraisal or tax assessment.
Comparison with Council Tax
The user enters the annual Council Tax they actually pay after current discounts or reductions, excluding arrears. The tool subtracts the proposed annual charge from that entered amount:
Entered annual Council Tax − proposed annual property charge.
A positive result is displayed as an indicative saving. A negative result is displayed as an indicative increase. The calculator uses the amount actually paid so that a single-person discount, Council Tax Support or another current reduction is not mistaken for a saving under the proposal. It does not predict which support, discount or relief an eventual policy would retain.
Published transition cap
Fairer Share also described limiting the initial increase for an existing owner-occupied primary residence to £1,200 a year (£100 a month), with the cap ending when the property is sold. The calculator always labels its main result as an uncapped headline-rate estimate. When the entered figures would exceed that limit, it also shows the maximum starting figure implied by the campaign's cap.
The optional multi-year projection does not apply the cap because the tool does not know when the property will be sold or whether an eventual scheme would retain the campaign's transition design. The cap is described in Fairer Share's published manifesto.
Ownership-period comparison
The optional projection holds the property value, Council Tax bill and proposed rate constant for the entire period:
- Proposed path = annual proposed charge × entered ownership years.
- Current path = entered Council Tax × years + user-entered SDLT.
User-entered SDLT is included only for an owner-occupied main residence because the published proposal says SDLT remains for second homes and non-resident buyers. For those higher-rate categories SDLT is excluded from both paths because it does not change the comparison. We do not calculate current SDLT automatically because rates and reliefs change and depend on personal circumstances.
Source hierarchy
- Legislation and official government publications.
- Evidence published by Parliament.
- The policy author's own current publications.
- Independent specialist analysis.
- Reputable news reporting.
- Commentary and social posts, used only as leads.
The rates and core treatment modelled here come from Fairer Share's August 2020 written evidence hosted by the UK Parliament Treasury Committee, last checked on 27 July 2026. They are not enacted law or a formal government tax calculation. News headlines never change the calculator by themselves.
Deliberate exclusions
- Property-price growth or decline after the latest available House Price Index month.
- Future Council Tax increases.
- Mortgage costs, rent changes or property yields.
- Locally variable rates.
- Deferral interest or eligibility.
- Future reliefs and transition arrangements beyond the separately disclosed £1,200 campaign cap.
- Behavioural changes by buyers, sellers or landlords.
- Scotland, Wales and Northern Ireland: this calculator concerns the proposal for England only.
- Undeveloped plots with housing permission, which the evidence also discusses but this residential calculator does not model.
News collection
The live news page uses several narrowly defined searches for terms including “0.48% property tax”, “Proportional Property Tax”, “Fairer Share” and combinations of Andy Burnham with property, land and Council Tax reform. It refreshes its cached results at least every 30 minutes when the site is in use.
Only a title, publisher name, timestamp and external source link are displayed. Duplicates are removed. Automatic classification into policy, analysis or reporting is a navigation aid and is not a judgement about accuracy.
Change control
A methodology change requires a dated primary or authoritative source. When a rate or material assumption changes, 048.TAX will update the calculator, this page's version number and the visible review date. Historic results are not stored.
Privacy by design
Manually entered tax-calculator values remain in the visitor's browser. If the optional home-value estimator is used, the browser sends only the full postcode directly to HM Land Registry to retrieve registered sales and the House Price Index. Dwelling type and optional address parts remain in the browser. The app does not save the search to a database or account and does not pass it to advertising, analytics or the news endpoint.