Tiller Runway — cut-order tier budgeting + downsize and retirement models

Spreadsheets gSheets Templates
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Overview

I’m retired, and the question I needed answered wasn’t “am I on budget this month?” - it was “if my income or portfolio took a hit, what would I cut, and in what order?” I couldn’t find a template for that, so I built one on my Tiller sheet.

Open source, live demo: preludecsm.github.io/tiller-runway (made-up household, every number fabricated)

Five report pages:

  • Cut-order tiers - every category tagged Tier 0 (never cut) to Tier 3 (elective) on the Categories sheet, with a waterfall showing which pool pays for each tier, in priority order.
  • Downsize model - could home sale proceeds sustainably cover rent? Real cap-gains and tax-benefit math, not a rule of thumb.
  • Retirement sustainability - what spending holds up, at what confidence, over 20–50 years.
  • Advisor PDF - same numbers, no individual transactions. Safe to hand to a CPA.

Installation

This isn’t copy-the-template-and-done. The sheet side uses standard Tiller tabs, plus Bucket/Tier columns on Categories and two custom tabs (Downsize Model, Portfolio Model) holding every assumption as editable cells. The reports themselves are generated by open-source Python that reads the sheet — so seeing your own numbers means a one-time setup on your computer.

The guide is written for people who’ve never done anything like it, and the README has full-page screenshots of every report so you can decide if it’s worth it first: github.com/preludecsm/tiller-runway

Copy/use/modify freely — MIT licensed.

Sample sheet (synthetic, view-only — File → Make a copy), see its Read Me tab.

Not financial, tax, or legal advice — every figure is a model output based on assumptions you control. Happy to answer questions, would be particularly interested in anyone trying this on their own data.

Mick Noordewier

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Looks very intriguing, and possibly something that would be useful to me as I get closer to retirement age. I read through the readme and install instructions but I’m still unclear on how it works. Seems like you add some additional sheets and columns to your Tiller Foundation sheet, and after setting up a Google service account, presumably you use Python to interact with the foundation template. But where do the ‘reports’ live? Are they somehow sheets in the Foundation template, are they local html files you open, or ?

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Good question. The reports don’t live in the sheet at all, and I should make that clearer in the README.

The flow is: the Python script reads your sheet, does the math on your computer, and saves ordinary .html files into a folder. You double-click one and it opens in your browser, like any saved web page. Nothing is written back to your sheet (the scripts only read it) and nothing is uploaded anywhere. The live demo you clicked is literally those same files, just parked on a free host so people can see them without running anything.

On getting started, something that wasn’t true when you asked - I just pushed a change based on your question:

Three of the five reports need no custom tabs at all. Financial Summary, Spending by Category, and Spending by Tier run against the standard Tiller tabs you already have. The only sheet change is adding two columns, Bucket and Tier, to your existing Categories tab - just typing values into cells.

The other two (Downsize, Retirement Sustainability) each need one custom tab. You don’t have to decide anything up front: if a tab isn’t there, the script skips that report, tells you which one and why, and builds the rest. The pages it does build say plainly that they’re a partial set, so you can’t mistake it for the whole thing. Add a tab later and that report starts appearing. They’re independent, so you can add either one, both, or neither.

So a reasonable first run is: get it working, add the Tier column, and look at the cut-order report on your real numbers. If it’s useful, keep going. If not, you’ve spent an evening and changed nothing about your sheet.

Happy to help if you get stuck. Post here and I’ll walk you through it.

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@Mick I like that you had a problem to solve and created the solution! I like that you provided a demo which really helped me see how the solution works. Great job. I hope I never need to use it. :grinning_face:

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I’ve read recently in WSJ the decisions people make in retirement to anticipate a market drawback, not wanting to liquidate equities at their low. They range from keeping 3 years cash (money market) to no backup at all, relying on total return. I figured my Tiller history could tell me more accurately what part of my spend would be covered by guaranteed income, so that I could decide, for example, what 3 years of living expenses would require beyond that. This also assists in choosing how to cut back.

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To prepare for my retirement, I manually analyzed my financial situation to determine where to reduce expenses. I did an export of all my income and expenses out of Empower (Personal Capital) and imported them into Excel. I manually developed a four year budget reduction plan. I quickly found that maintaining the manual spreadsheet too time consuming. I discovered Tiller and easily made the switch. Your solution will be very helpful to anyone planning to retire or has a significant loss of income.

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Really good stuff Mick. I’m on the verge of retirement, so your thoughtful template is so timely for me. I’ll give it a try and let you know what I think.

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I see how this can be useful. I’ll try it out at some point.

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Chiming in here…Really excellent and a thoughtful (meaning it’s got me thinking) of ways to leverage the transaction register for alternative reporting. My Asset Allocation model, ALM model, and drawdown model live in Apple Numbers and I actually manually enter summary data from Tiller as I need. Your integrated solution has me thinking…

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