How US Savers Optimise a 401k and IRA
For US professionals with a 401k · Based on Donegans Three-Decision Investing Framework
// TL;DR
US professionals can use the Donegans Three-Decision Framework to make sense of 401ks, IRAs, and HSAs by treating each as an Account layer wrapping a Fund, held on a Platform. It shows you how to capture your full employer match (free money), select the lowest-cost passive global or total-market index fund inside your plan, and decide when to open a separate IRA for extra tax-advantaged space. If you're within a few years of retirement (the Bridge It phase), it explains adding a spending buffer alongside your growth engine.
Why should US professionals use the Three-Decision Framework?
American investors face an alphabet soup of accounts — 401k, 403b, IRA, Roth, HSA — plus endless fund menus. The Donegans Three-Decision Framework simplifies all of it into three choices: the Fund (your growth engine), the Account (the tax container), and the Platform (the provider holding it). Your 401k is a Defined Contribution Investment Pot, so you're responsible for what it owns and how much it grows.
The framework works identically in the US and everywhere else because it targets structure, not products.
How do I capture the employer match first?
Free Money First is non-negotiable. Before anything else, contribute enough to your 401k to capture your full employer match — leaving it on the table is turning down a guaranteed return. This is Decision 2 (Account): prioritise tax-advantaged space in order — the 401k up to the match, then consider an IRA or HSA for additional tax-advantaged room, then more 401k.
Once free money is captured, you can decide whether your 401k's fund menu is good enough or whether extra contributions should flow into a lower-cost IRA at Vanguard, Fidelity, or Charles Schwab.
How do I choose the right fund inside my 401k?
Apply the Growth Engine Checklist to every fund option: Broad, Global, Passive, Low cost, Understandable. Within many 401k menus your best choice is a total world index fund or, if that's unavailable, an S&P 500 index fund. Remember how global is your global fund — an S&P 500 fund is 500 US companies only, while a total-world fund like VT (Vanguard Total World Stock) captures developed and emerging markets.
If your only option is an S&P 500 index fund, don't agonize — apply the Good Enough Stamp and stop. For extra diversification, a self-directed IRA lets you hold a truly global fund. Beware home country bias: US markets have done well, but familiar doesn't guarantee future outperformance.
How does my retirement timeline change my allocation?
Identify your investing phase:
- Build It — years from retirement: hold 100% growth engine.
- Bridge It — within 3–5 years of stopping work: add a spending buffer (bonds or a money market fund) alongside the growth engine to protect against short-term volatility.
- Live From It — drawing down: keep the growth engine running, withdraw from the buffer, and rebalance.
The growth engine — your global index fund — never disappears. In Bridge It and Live From It you simply add the buffer alongside it.
When should I use a platform outside my 401k?
Your 401k platform is chosen by your employer, so you can't shop it — but your IRA platform is your choice. Evaluate platforms on three criteria: Trustworthy (regulated, client assets segregated, established), Has the right Account and Fund (offers an IRA and a low-cost global index fund), and Fees low and usable (compare fixed vs percentage fees; avoid percentage-based advice fees). Vanguard, Fidelity, and Schwab all typically offer very low-cost total-market funds.
Next step: Check your 401k contribution rate today and confirm you're capturing your full employer match. Then look up the expense ratio of your current fund — if it's high or actively managed, switch to the lowest-cost passive index option in your menu, and consider opening an IRA for additional global exposure.
// FREQUENTLY ASKED QUESTIONS
Should I max my 401k or open an IRA first?
Capture your full 401k employer match first — that's free money you can't beat anywhere. After the match, an IRA or HSA often offers lower-cost fund choices and more flexibility, so many investors fund those next before returning to max out the 401k. The order is: match, then best tax-advantaged space, then more contributions.
Is VT a good fund for a US investor?
VT (Vanguard Total World Stock) is a strong single-fund growth engine because it covers both developed and emerging markets globally — the Global All-Cap equivalent for US investors. It passes the Growth Engine Checklist as broad, global, passive, low-cost, and understandable. If your 401k only offers an S&P 500 index fund, use it and get global exposure through a separate IRA holding VT.
Do I need bonds in my 401k in my 40s?
Probably not if you're in the Build It phase, still years from retirement — hold 100% growth engine. You add a spending buffer of bonds or a money market fund only in the Bridge It phase, roughly 3–5 years either side of stopping work. Adding bonds too early can drag on long-term growth while you still have decades to ride out volatility.