How the calculators work
Calculator Methodology
The exact assumptions and formulas behind every calculator on this site, published openly so you can check them.
Current assumptions (2025/26 tax year, last checked 6 April 2025)
| Assumption | Value | Source |
|---|---|---|
| Free shares annual limit | £3,600 | ITEPA 2003, Sch. 2 |
| Partnership shares annual limit | £1,800 or 10% of salary, lower | ITEPA 2003, Sch. 2 |
| Maximum matching ratio | 2 matching shares per 1 partnership share | ITEPA 2003, Sch. 2 |
| Employee NIC rate (illustrative) | 8% | Confirm current rate before relying on this figure |
| Full tax-free holding period | 5 years | HMRC ETASSUM |
Main calculator formulas
partnership_contribution = min(monthly_input × 12, 1800, 10% × salary)
matching_value = partnership_contribution × matching_ratio (ratio capped at 2)
free_shares_value = min(free_input, 3600)
total_annual_value = partnership_contribution + matching_value + free_shares_value
tax_saved = partnership_contribution × (income_tax_rate + employee_NIC_rate)
future_value = total_annual_value × (1 + growth_rate) ^ years
What the calculators do not model
Capital Gains Tax on growth after shares leave the trust, employer-specific plan rules (e.g. non-standard forfeiture terms), and any changes to HMRC rules since our last review date. All figures are estimates for educational purposes only.
Where your data goes
Every calculation happens in your browser. Nothing you type into a calculator is sent to or stored on our servers.