I have not found a good free financial planning template for modelling a 40 year drawdown, inflation, state pension, taxes etc. Excel and roll your own seems to be the way to go. As we all know hell is other people's spreadsheets. As you try and build it you run up against a set of questions which you need a good handle on. My initial research on life beyond annuities led me to look at safe withdrawal rates - back testing and montecarlo analysis on old equity markets of the "how much could I have with a given near zero chance of running out" question but this now feels actually to be the wrong way up. The proposed budget matters more to understand income flexibility which impacts the approach and the available income. That asks a bunch of hard personal questions you need to answer for a scenario to be realistic. Here are the ones I have come up with. Whether you plan your own or talk to an IFA you'll still need a POV on these. Yours will vary.
1 Activity - building a better version of a long term budget – what is really needed as regular income and for "nice to haves" and one offs (discretionary). This can then be used to gain understanding with back testing and peer comparison of how risky a planned indexed withdrawal rate meeting this budget profile will be when viewed against a back test of difficult periods (market corrections, slumps, high CAPE at retirement etc.). From this you can get to be comfortable with the idea of drawdown for your "cohort" (age based in terms of market timing.
2 Property assumptions – developing a scenario for where to be living and when over the next 40 years (Good luck with that) or some assumptions on the capital tied up and cost relative to now.
3 Further assumptions on cars, travel, toys - trains boats planes guitars and topics like helping children and parents and how these discretionary items fit into the base budget
4 Are there any potential inheritance impacts (inward, outgoing, tax assumptions, potential use of deeds of variation etc. which are affected by when these things happen
5 Care - the big one - what assumptions do you make on about care costs. Unknown political changes inbound to socialise this risk (for both good and ill). I suspect I will be asked to pay for this whether I need it or not via new taxes to socialise - which will materially hit the budget and then be means tested as to be ineligible to receive it without further co-payment/cross-subsidy as now. So a shit show – but it pretty much has to work like that to be affordable overall. Or carry on as we are with the various postcode injustices uncapped personal costs and other problems that causes. Not good either.
6 Handling a return of the 1970’s. Understanding EU / Irish / Other contingencies against a full blooded revisiting of that ugly era. Waste it first - consume savings excess and telling the tax man to feck off being a fall back of last resort still available with UK residency and domicile.
7 Check any emerging plan for common sense IHT planning based on today’s rules. This particular tail must not be allowed to wag the overall dog but there is no need to be wantonly stupid about it either.