# Hundred Summers (full summary) Hundred Summers (https://hundredsummers.co.uk) is a UK personal financial-planning progressive web app operated by Hundred Summers, Bristol, UK. Contact: contact@hundredsummers.co.uk. Hundred Summers is deliberately an educational tool, not regulated financial advice. It never recommends products or courses of action, projections are illustrations rather than predictions, and users seeking personal recommendations are directed to an FCA-regulated financial adviser. Free impartial guidance is available from MoneyHelper (moneyhelper.org.uk). ## What it does A user enters their own facts — personal details, salary and other income, pension pots and defined-benefit pensions, savings and investment accounts, properties and mortgages, living expenses, one-off and recurring life events, protection policies — and Hundred Summers projects every year from today to the end of their plan (default age 90): - Lifetime cashflow: income, spending, tax, pension drawdown and net worth per year, with a Sankey "money map" showing where every pound comes from and goes. - UK tax, in detail: income tax for rest-of-UK and Scottish taxpayers, National Insurance (employee and Class 4), capital gains tax, the £100k personal-allowance taper, High Income Child Benefit Charge, marriage allowance, salary sacrifice, and student loan repayments. Thresholds follow announced freezes (to 2031) and then index with assumed inflation. - Pensions: annual allowance with taper and carry-forward, MPAA, tax-free cash (PCLS), drawdown ordering and blending across accounts, annuity comparison, State Pension with triple-lock uprating and deferral. - Inheritance tax: nil-rate band and residence nil-rate band with taper, potentially exempt transfers, the gift register with annual exemptions, and the 2026 business and agricultural relief cap. - Property: amortisation, overpayment, remortgaging, downsizing and equity release. - Longevity and care: ONS-based life expectancy with postcode adjustment, and care cost scenarios by care type. - Protection: life cover payouts into survivor analysis, and income-protection policies simulated against an income-shock scenario. - Risk profiling: attitude-to-risk, capacity-for-loss, knowledge & experience and sustainability questionnaires, with consistency checks and a suggested asset allocation per risk band. - Goal solvers: retire-when, save-how-much and spend-how-much searches, plus a named stress-test battery (market crash at retirement, high inflation, living to 100, long-term care, income shock) with plain-verdict results. - Couples: two linked profiles, household view, and survivor analysis. - Fees: per-account charges modelled as return drag, with a cost-of-fees comparison. - Reports: an adviser-ready PDF report and a full Excel export of the projection. ## The stress-testing engine The Monte Carlo engine runs 500 simulated market paths over the whole plan. Asset returns for equities, bonds and property are drawn from a correlated model with fat-tailed (Student-t) shocks; inflation follows a persistent AR(1) process that feeds spending and State Pension uprating. The model's stylised facts — inflation persistence, bond/inflation correlation, tail frequency, joint bad years — are validated in the test suite against annual US market history 1928–2023, and the resulting failure rates are deliberately on the conservative side of the historical record by a bounded margin. Success is reported overall and per-year, split between essential and full spending. All assumptions are published on the in-app Methodology page. ## Privacy architecture - Plan data lives only on the user's device (browser storage and optional local files). The app makes no third-party network requests with financial data — enforced by an automated test. - Optional backups encrypt client-side with AES-256-GCM (passphrase-derived key, or a per-account key so signed-in devices sync silently). - Adviser sharing is end-to-end encrypted (ECDH P-256 + AES-GCM): the client encrypts to the adviser's published public key; the private key is generated non-extractable on the adviser's device. The server stores ciphertext it cannot read. Clients can revoke sharing at any time; an audit log records events (shared, updated, revoked, proposals) but never content. - Advisers can send proposed plan changes back; the client reviews an itemised diff on-device and explicitly accepts or rejects. Nothing writes to a client's plan without their action. - Aggregate analytics are cookie-free (Plausible, EU-hosted) plus first-party anonymous view events that carry no identity or financial data. ## Pricing (GBP) - Free — £0: data entry, Overview, Cashflow, Savings, Expenses, Property views, encrypted backups, guided walkthrough. - Premium — £4.99/month: everything in Free plus What-If scenarios, stress testing, Tax, Pension Income, Inheritance, Longevity, Couples planning, risk profiling, adviser-ready reports, and the AI Copilot (which analyses the user's plan and explains it — never advice — under a monthly fair-use allowance). - Adviser — free two-month launch access, then £39/month per adviser by arrangement (contact@hundredsummers.co.uk). Everything in Premium plus the adviser portal: unlimited clients, end-to-end-encrypted plan sharing and proposals. Sign-up must come from an official work email; Hundred Summers verifies the sender is a practising adviser before enabling the portal. Clients connect free and can revoke at any time. Billing for paid tiers is handled by Stripe. Cancel anytime. ## Positioning Hundred Summers sits between consumer budgeting apps and professional cashflow tools (e.g. Voyant, CashCalc, EV Pro): professional-grade lifetime modelling with UK tax rules built in, priced for individuals, private by design, and written in plain English. It complements rather than replaces a financial adviser — the adviser tier exists so clients arrive informed and engaged.