Find your Tax Valley and model Roth-conversion headroom

If you have money in a Traditional 401(k) or Traditional IRA, you’ll eventually pay income tax on every dollar you withdraw. When you take it out matters as much as how much you have. There is often a window — a few years after you stop working and before Social Security + Required Minimum Distributions kick in — when your taxable income drops. That window is your Tax Valley, and it can be worth modeling before you decide whether any pre-tax retirement money should move into a Roth.

This walks you through finding your specific Tax Valley in GlidePath and seeing how Roth-conversion headroom changes the projected tax stack over your lifetime.

What you’ll learn

What “Tax Valley” means in plain English (and why it’s a thing)
How to find yours on the /Retirement page
How much conversion room appears year by year before the next federal bracket (the bracket headroom)
Why the valley is a window to evaluate Roth conversions before RMDs hit
Why this matters even more if you’ll have significant RMDs (which start at 73 or 75, depending on your birth year)

Before you start

You should have these set up first:

The Partners page — your birth dates drive the tax-bracket projections
The Accounts page — at least one Traditional 401(k) or Traditional IRA with a balance
The Retirement page basics — your target retirement age, expected Social Security claim age

You don’t need perfect numbers. Tax Valley analysis is fundamentally about windows of opportunity, not point estimates — getting your situation 80% right is enough to know whether to keep reading or to call a CPA.

What’s a Tax Valley, in two paragraphs

Here’s the lifetime arc of taxable income for a typical retiree:

Working years (your 30s-60s) — high taxable income from your salary, putting you in 22%, 24%, or 32% federal brackets
Early retirement (your 60s) — paychecks stop. If you haven’t started Social Security yet and don’t have to take RMDs yet, your taxable income drops to maybe a small pension + a small amount of interest. You might be in the 10% or 12% bracket.
Late retirement (mid-70s+) — Social Security + Required Minimum Distributions force taxable income back up. Often into the 22% or higher bracket again, sometimes higher than you ever were while working.

That dip in the middle is the Tax Valley. Dollars converted from Traditional to Roth during a lower-bracket year may face less federal tax pressure than dollars forced out later by RMDs. Same dollar, different year, potentially different tax stack.

Step 1 — Open /Retirement and find the Tax Valley chart (1 min)

In the desktop app, open Retirement (it’s under Planning in the top nav). Scroll down past the Monte Carlo section to the “Tax valley & Roth conversion window” panel.

You’ll see a year-by-year stacked bar chart of your projected taxable income, color-coded by source:

Ordinary income (salary, pension)
Social Security taxable portion
Investment income (interest, dividends, realized gains)
RMDs (Required Minimum Distributions, starting at 73 or 75 depending on your birth year)

The Tax Valley is the band where the stack is shortest — usually a few years between when you stop working and when SS + RMDs hit full force. GlidePath spells it out in plain English: the summary line up top reads “Your Tax Valley spans N years,” the panel explains why those years can be lower-tax years worth modeling, and the table below it lists each specific valley year with the bracket you’d be in.

Step 2 — Read the bracket-headroom number (1 min)

Below the chart, GlidePath shows the bracket headroom for each valley year. Bracket headroom is the answer to: how many more dollars of taxable income can I have this year before I jump from the 12% bracket to the 22% bracket?

For a typical pre-retiree, the headroom is $30,000 to $80,000 per year during the valley. That’s how much taxable conversion room may fit before the next bracket, before layering in Social Security taxation, IRMAA, NIIT, and state-tax considerations.

If you have $400K in a Traditional 401(k) and 7 valley years, that’s $400K spread across 7 years = ~$57K/year. GlidePath shows whether that rough annual amount fits the modeled federal brackets before you and your preparer decide whether any conversion plan makes sense.

Step 3 — Decide how much to convert (and run it by a CPA)

GlidePath shows you the valley and the cumulative bracket headroom. It does not auto-plan your conversions or promise a dollar savings figure — picking the amount is your call, and a great thing to confirm with a tax pro, because a Roth conversion has real second-order effects the headroom number alone doesn’t capture:

The Social Security “tax torpedo” — a conversion can push more of your Social Security into taxable income, so the true cost is sometimes higher than the headline bracket suggests.
IRMAA — a large conversion can raise your Medicare premiums two years later.
ACA subsidies — before age 65, a conversion raises the MAGI your premium tax credit is based on, and can shrink the subsidy.

So the workflow is: GlidePath shows the modeled window and roughly how much federal bracket room appears; you and your preparer decide whether any amount fits after the second-order effects are considered.

Step 4 — Do the conversion at your brokerage, then re-check next year

A Roth conversion happens in your brokerage account (Fidelity, Schwab, Vanguard, etc.), not in GlidePath — you tell them to move $X from the Traditional IRA/401(k) into the Roth. You’ll owe ordinary income tax on the converted amount for that year, which is why the year-by-year tax stack matters.

Then update your balances in GlidePath and the valley re-draws for the next year. If you choose to convert in more than one year, the next year’s window reflects the lower pre-tax balance and the latest assumptions.

What just happened

You did three things most people never get around to:

Identified a potentially lower-tax window — a specific multi-year range when your taxable income may dip before RMDs and Social Security change the stack
Saw how much pre-tax money could fit during that window before the next federal bracket — often tens of thousands per year of bracket headroom
Got a concrete starting point for your CPA — “here’s the modeled window and roughly how much federal bracket room appears; what would it take to actually do this?”

This is the kind of retirement-tax modeling many basic budgeting tools never show. It is not a curiosity; it is a practical worksheet for a preparer conversation.

What this is not

It’s not tax advice. GlidePath shows you bracket arithmetic and conversion windows. Whether to actually execute a conversion strategy depends on factors specific to your situation that you should walk through with a CPA or fee-only fiduciary advisor — IRMAA Medicare premium thresholds, state tax considerations, anticipated changes in tax law, your willingness to pay tax up front, and so on. See the tax disclaimer for the formal version.
It’s not legal advice on Social Security claiming. The Tax Valley analysis assumes a specific Social Security claim age you’ve set on /Retirement; the claiming choice is a separate decision that depends on your earnings history, health, and spousal coordination.
It’s not a guarantee. Tax law changes. Brackets get adjusted, sometimes dramatically. GlidePath uses the most recent IRS tables we have; if Congress reshapes the tax code, the conversion math may shift.

Ask Glide about this

Try: “Why can a Roth conversion look different before RMDs than after?” or “What’s the difference between a Roth conversion and a Roth contribution?” Glide will walk through both in plain English without seeing your actual numbers.

Where to next

Track a balance transfer end-to-end — for the debt side of the planning conversation
More planning tutorials coming — ACA bridge cost modeling, Social Security claim-age math, retirement Monte Carlo with sequence-of-returns risk