A local-first desktop app for UK retirement and long-term financial planning. All your data stays on your machine — no cloud, no accounts, no telemetry.
Status: alpha. The simulation engine, UK tax modelling and the full UI are working end-to-end. APIs and schemas may still change between minor releases.
Most retirement calculators are spreadsheets, simplified web tools, or financial-advice products that gate the interesting features behind a paywall. Planner is a serious projection engine wrapped in a calm, opinionated UI:
- Year-by-year deterministic projection — no hand-wavy "average return". Every year has explicit income streams, drawdowns, growth, and per-person UK tax.
- Scenarios — Compare a base plan to "retire at 60", "downsize the house", or any field-level override.
- Stress tests + Monte Carlo — Sequence-of-returns risk, market crash, early death, high inflation, lower returns.
- Tax-aware — UFPLS vs PCLS-upfront SIPP strategies, Marriage Allowance, personal-allowance taper, ISA tax-free, cash-as-savings.
- Local-first — SQLite on your machine. The whole simulation runs in the main process; the renderer only draws.
| Overview | Strategy |
|---|---|
 |
 |
| Assets | Expenses |
|---|---|
 |
 |
Captured via
bash scripts/screenshots.sh— builds the renderer, runs Electron in screenshot mode, navigates each tab and writes the four PNGs todocs/images/.
- Household-level projection with per-person UK income tax (Personal Allowance taper, basic / higher / additional bands).
- Marriage Allowance transfer between spouses where eligible.
- Accumulation phase with personal + employer pension contributions and pro-rata for birth-month-aware retirement years.
- Drawdown phase anchored on the primary earner's retirement: birth-month timing controls when household drawdown actually starts.
- SIPP strategies — UFPLS (25%/75% on every withdrawal) or PCLS-upfront (crystallise the whole pot at retirement; remaining 75% fully taxable). The engine recommends whichever produces lower lifetime tax.
- Time-banded spending — go-go / slow-go / no-go periods, inflation-linked. The earliest period auto-extends back to cover early retirement.
- One-off events — windfalls (inheritances, lump sums), planned expenses (renovation, car, gifts).
- Scenarios — clone the base plan and override any field (retirement age, spending, growth, custom assumption set / expense profile).
- Wealth burndown chart — household assets across the projection, with retirement-year markers.
- Cash-flow chart — annual income sources stacked with bridge-year drawdowns, and a toggleable spending-target line.
- Stress tests — high inflation, lower returns, early death, market crash. Shows the delta vs the base projection.
- Monte Carlo — N iterations with normal-distribution returns; reports success probability + p10/p50/p90 end assets. Captures sequence-of-returns risk.
- Recommendations engine — quantified spending cut, asset depletion runway, defer-retirement, tax taper exposure, optimal SIPP crystallisation.
- Electron desktop shell (macOS / Windows / Linux).
- SQLite via
better-sqlite3and Drizzle ORM. - React 19 + TanStack Router + TanStack Query.
- Tailwind v4 + shadcn/ui + base-ui.
- Recharts for charts.
- Dark mode with a header toggle (and respects
prefers-color-scheme). - View Transitions API for smooth route switching.
- Lazy-loaded route chunks (~140 kB gz initial bundle).
Anyone who:
- Wants to model a UK retirement plan with their actual numbers, not a what-if calculator demo.
- Cares about tax efficiency (PCLS vs UFPLS, Marriage Allowance, personal-allowance taper).
- Runs more than one scenario ("what if I retire at 60?") and wants to compare them.
- Won't put their household balance sheet into a hosted app.
git clone https://github.com/<your>/planner.git
cd planner
bun installbun run startVite serves the renderer at http://localhost:3000; Electron loads it. Hot-reload works for both.
bun run testbun run buildOutputs an installable app via electron-builder.
planner/
├── public/ # Electron main process (CommonJS)
│ ├── electron.js # window + IPC + CSP
│ ├── preload.js # exposes window.api to the renderer
│ ├── ipc/ # IPC handlers (per resource)
│ ├── db.js # bundled SQLite + Drizzle (built from src)
│ └── engine.js # bundled projection engine (built from src)
│
├── src/
│ ├── components/
│ │ ├── layout/ # AppHeader, PlanLayout, StatCard, ScoreDonut
│ │ └── ui/ # shadcn primitives (Button, Slider, Select, etc.)
│ │
│ ├── contexts/ # PlanContext, ThemeContext
│ ├── hooks/ # TanStack Query hooks per resource
│ │
│ ├── pages/
│ │ ├── index.tsx # / — redirects into the active plan
│ │ ├── onboarding/ # multi-step plan creation
│ │ └── plan/[id]/
│ │ ├── _shared/ # ScenarioModal, SavingsBurndownChart, utils
│ │ ├── overview/ # /overview — hero stats, charts, recommendations
│ │ ├── assets/ # /assets — accounts, income streams, one-off incomes
│ │ ├── expenses/ # /expenses — spending baseline + life-stage overrides
│ │ ├── strategy/ # /strategy — drawdown presets, stress tests, MC, table
│ │ └── settings/ # /settings — household, assumptions, tax policy
│ │
│ ├── services/
│ │ ├── db/ # Drizzle schema + migrations (source of truth)
│ │ └── engine/ # the projection engine + types
│ │
│ ├── tests/integration/ # IPC-end integration tests (in-memory SQLite)
│ ├── main.tsx # renderer entry
│ └── router.tsx # TanStack route tree
│
├── .ai/ # design artifacts, planning docs, research
└── docs/ # ARCHITECTURE, FEATURES, NEW-USER-GUIDE, TROUBLESHOOTING, images/
- ARCHITECTURE.md — process model, data flow, engine internals, route tree, with diagrams.
- CHANGELOG.md — release history.
- AGENTS.md — instructions for AI agents working on the codebase.
TBD. Until a licence is added, the contents of this repository are © Mark Fairhurst, all rights reserved.