About ODOpt
ODOpt is a free suite of UK tax and retirement planning tools — built to give ordinary people the kind of modelling that financial planners use, without the fees or the jargon.
Every tool is free to use, with no sign-up. The tools are supported by advertising; if you'd rather not see ads, an optional subscription removes them. That's the whole model.
What we build
ODOpt is a growing collection of UK-focused financial tools, including a Monte Carlo Retirement Planner, an Owner-Director Salary & Dividend Optimiser, a day-rate simulator, payslip and annual tax calculators, and a UK tax changes dashboard. You can see the full list on the tools page.
The tools run in your browser, use current UK tax rules, and are designed to be honest about uncertainty — the retirement planner, for example, runs thousands of simulated futures rather than projecting a single optimistic line.
Who we are
ODOpt is built and operated by Oosthuizen Consulting, a UK business based in St Albans, Hertfordshire, and founded by Lambertus Oosthuizen. The project grew out of a simple frustration: good retirement and tax modelling was locked behind adviser fees or buried in spreadsheets, and the free calculators online were too simplistic to be trusted with real decisions.
We build the tools we wanted to use ourselves — accurate, UK-specific, and clear about what they can and cannot tell you.
How we approach it
- UK-calibrated. Built around UK tax rules, the State Pension, ISAs and pensions — not repurposed US research.
- Model-driven. Where the future is uncertain, we simulate it rather than assuming a single outcome.
- Plain English. The guides and blog explain the concepts behind the tools so you can make informed decisions.
- Free and open to everyone. No paywall on the tools; no sign-up required to use them.
Important — not financial advice
ODOpt provides general information and modelling tools, not personal financial, investment, or tax advice. The outputs are estimates based on the assumptions you enter and on published tax rules, and they may not reflect your individual circumstances. Always consider taking regulated advice before making significant financial decisions. See our disclaimers for detail.
Get in touch
Questions, feedback, or found a calculation you disagree with? We'd like to hear from you. Email support@odopt.uk or use the contact page.