Each account is a card. The fields below define how the engine taxes growth, where it can deposit surplus cash, and how it draws money down in retirement.

Fields

• Account Name - used in Proof tables and events.
• Account Type - controls tax and withdrawal handling.
• Allocation (pie icon) - the mix by asset class within the account.
• Fees (%) - annual drag applied to account growth.
• Initial Cost Basis (Brokerage) - the portion of your brokerage balance that is original contributions, not gains. Entered and shown in your plan's own currency. It does not appear on a Dutch plan, where personal capital gains are not taxed; on a BV it appears as Initial Book Value and drives the company's corporate tax instead.
• Person - ownership mapping for timing and tax behavior.
• Balance - total account value used to scale allocation amounts.
• HSA Coverage (HSA only) - Self or Family for contribution logic. A Cash Flow Priority that targets the HSA and names a Job as its paycheck is taken out before income tax and FICA; see HSA contributions through payroll.

529 College Savings Plan

A 529 is quarantined from general spending: no withdrawal order and no shortfall will ever raid it. The only thing that draws on it is an expense that names it as its funding account, and only an Education Expense does so tax-free - any other expense type pointed at a 529 is a non-qualified withdrawal, with the earnings taxed as income plus a 10% penalty. Picking a Beneficiary links the account to a dependent for FAFSA reporting and auto-fills the expected first withdrawal year; it does not by itself cause a single dollar to leave the account. A 529 with no Education Expense drawing on it is flagged in Plan Diagnostics after a run, with a button that opens the account so you can create the expense from there.

A 529 keeps the mix you gave it and does not take part in portfolio-wide rebalancing: the household allocation target is measured against your other accounts, and the 529 is rebalanced back to its own starting proportions each year. Sleeves you left at zero stay at zero.

If the beneficiary has a cost of attendance and nothing draws on the account yet, the editor offers a Create college expense button that builds the Education Expense for you, prefilled from the child's college years and cost. See People tab and Expense types.

I Bonds (TreasuryDirect)

An I Bonds account holds Series I savings bonds and nothing else. Enter its current value as the balance, what you paid as the Purchase Price (basis), and the bonds' Fixed Rate. What the simulation models:

• Growth: each year the balance grows by that year's inflation plus the fixed rate, using the inflation of the historical period or Monte Carlo path being simulated. It never shrinks: a deflation year earns 0%, not a loss.
• Federal tax, deferred: nothing is taxed while you hold the bonds. When the simulation redeems them, the interest share of the redemption (the part above your purchase price, in proportion) is federal ordinary income and counts toward your AGI, MAGI and the Net Investment Income Tax.
• No state tax: I bond interest is exempt from state and local income tax in every state.
• Buying more: only a cash flow priority buys I bonds. Surplus cash and rebalancing never add to the account, so without one the balance only grows by its interest. The account editor's Buy I bonds each year button sets one up. Purchases are capped at $10,000 per person per calendar year across all of that person's I bond accounts, so each account has one owner. A priority that asks for more deposits $10,000 and the rest moves to your next priority.
• Spending: I bonds can fund spending like a brokerage. To keep the tax deferral going while other money lasts, place the I bond account after your brokerage in your withdrawal order. With no order set, they are drawn alongside your other accounts.
• I bonds stay out of portfolio rebalancing and do not count toward your target allocation.

What the simulation does not model:

• The 12-month lockup after purchase, and the 3 months of interest forfeited on bonds redeemed before 5 years.
• The 30-year final maturity, when deferred interest becomes taxable whether or not you redeem.
• The education exclusion, which can make the interest federally tax-free for qualified college costs.
• A separate fixed rate per purchase: one rate applies to the whole account, including new purchases.
• Paper I bonds bought with a tax refund, reporting interest yearly instead of deferring it, and EE bonds.

The yearly rate is inflation plus the fixed rate. TreasuryDirect's composite rate also adds a small cross term, so with a 1.2% fixed rate and 3% inflation the Treasury pays about 4.218% where the simulation uses 4.2%.

Rule of 55 (penalty-free age)

Money in a 401(k) or 403(b) is normally penalized 10% if you withdraw it before age 59½. The Rule of 55 is an exception: if you leave an employer in or after the calendar year you turn 55 (50 for qualified public safety employees), that employer's plan can be spent penalty-free from then on. A 401(k), Roth 401(k), 403(b) or Solo 401(k) has an optional Penalty-free age picker for this, listing each age as the year you reach it. Keep the 59½ default when the rule does not apply; pick the year you turn 55 (or 50) and the simulation stops charging the penalty on that account from that year, and spends it ahead of penalized money.

When a Job linked to the account through a cash flow priority ends in a year you are 55 or older, the editor suggests the Rule of 55 with an Apply button. It never sets the field on its own, because FIREproof cannot know three things only you do:

• It applies only to the plan of the employer you left, not to an older 401(k) from a previous job.
• It is lost if you roll the money into an IRA. An IRA never qualifies.
• Some plans refuse partial withdrawals, which makes the rule hard to use in practice.

Once set, the account card shows a Rule of 55 chip, and a withdrawal from it before 60 carries an info icon in the year-by-year explaining why no penalty applied.

SIPP and Plan de Pensiones (access age)

A UK SIPP cannot be drawn before the minimum pension age: 55 through 2027, 57 from 2028. A Spanish Plan de Pensiones is treated as locked until 65. Before that age the simulation does not use the account for spending at all. If nothing else can fund a year, that year fails rather than drawing money you could not reach. Both accounts have an optional Accessible from picker for an earlier age you do have: a UK protected pension age, ill health, or Plan de Pensiones contributions more than ten years old.

In a UK plan, 25% of each SIPP withdrawal is tax-free until you have taken the Lump Sum Allowance (GBP 268,275 per person); the rest is taxed as income. FIREproof assumes your SIPP has not been crystallised and that none of your allowance is used yet. If you already took your tax-free cash, the simulation overstates what you can draw tax-free.

Solo 401k (self-employed retirement plan)

A Solo 401(k) (also called one-participant 401(k), Individual 401(k), Uni-K, or Solo-K) is a 401(k) designed for self-employed people with no full-time non-spouse employees. FIREproof supports both Traditional Solo 401k and Roth Solo 401k as account types.

Who is eligible

• Sole proprietors reporting income on Schedule C.
• Single-member LLCs taxed as sole proprietorships.
• S-corp owner-employees who pay themselves W-2 wages.
• A spouse who earns income from the business may also participate; any other full-time non-spouse employee disqualifies the plan.

The two-hat contribution structure

Because you are both the employee and the employer, you contribute in two capacities. The two limits stack, up to the §415(c) per-account cap.

• Employee elective deferral (§402(g)): a flat dollar limit that is shared across every 401(k)-style account you own (W-2 401k, 403b, TSP, and the Solo 401k all draw from the same bucket).
• Employer non-elective contribution: a percentage of net self-employment earnings. The percentage depends on entity type.

2025 limits

The 60-63 enhanced catch-up is the SECURE 2.0 "super catch-up". It applies in the calendar years you are 60, 61, 62, or 63, and snaps back to the standard 50+ catch-up at age 64.

Employer non-elective contribution caps depend on entity type:

• Schedule C / sole prop / single-member LLC: roughly 20% of net self-employment earnings after deducting one-half of self-employment tax. (The on-paper 25% rate gets reduced to ~20% once the contribution itself is netted out of the base.)
• S-corp owner-employee: 25% of W-2 wages from the S-corp.

Traditional vs Roth Solo 401(k)

• Traditional Solo 401k: contributions reduce income tax in the year contributed. Note that the non-elective employer contribution reduces income tax only. It does not reduce self-employment (SE) tax, because SE tax is computed on net earnings before the retirement contribution deduction. Withdrawals are taxed as ordinary income.
• Roth Solo 401k: contributions are made post-tax. Under SECURE 2.0 §604, the employer non-elective portion can also be designated as Roth (post-tax), not just the employee deferral. Qualified withdrawals are tax-free.

Required minimum distributions

• Traditional Solo 401k: RMDs apply at the owner's SECURE 2.0 start age, which depends on birth year: 73 for people born 1951 through 1959, 75 for anyone born in 1960 or later. The same rule applies to every other pre-tax US account.
• Roth Solo 401k: no RMDs during the owner's lifetime (SECURE 2.0 §325, effective 2024). This mirrors the long-standing Roth IRA treatment and removes the historical "roll Roth 401(k) to Roth IRA to escape RMDs" workaround.

Pensioen and Lijfrente (Netherlands)

Available when Tax Country is set to Netherlands. Both are pre-tax pension wrappers: contributions reduce your Box 1 income, the balance is exempt from the Box 3 wealth tax while held, and each payout is taxed as Box 1 income. Pensioen is the employer scheme (fund it from a Job); Lijfrente is the personal annuity.

Unlike every other account type, these pay out on a schedule you set and cannot be spent freely. Pick a payout age and either a lifetime or fixed-term style in the account editor. They do not appear in your withdrawal order, and a year that could only be funded from one of them fails rather than draining it. See the Netherlands tax page for the full picture.

BV (Personal Holding Company)

Available when Tax Country is set to Netherlands. A BV (besloten vennootschap) is not a tax wrapper like an IRA - it is a separate company that happens to hold your investments, and FIREproof taxes it as its own taxpayer.

• Two layers of tax, in order. The BV pays Dutch corporate income tax (19% on the first EUR 200,000 of its profit, 25.8% above) each year, and then you pay Box 2 tax on whatever it distributes to you (24.5% / 31%). Combined that is roughly 38.8% at the low rates and 48.8% at the top.
• Money left inside pays only the first layer. That deferral is the point of the structure. Unrealized growth is not taxed at all.
• Box 2 taxes the whole distribution, not just the gain inside it - the company's gains were already taxed at the corporate layer.
• No contribution limit. Funding a BV is a capital contribution, not an annual allowance, so it is out of band for the simulation. Surplus income is not routed into a BV automatically; it goes to your brokerage.
• Set a cost basis, exactly as you would for a brokerage account. It determines the profit the BV realizes when it sells, which is what the corporate layer is charged on.
• No RMDs. A BV is not a retirement account.

Full detail, including loss carryforward and what is approximated, is on the Netherlands tax page.

Inherited IRAs (SECURE-Act 10-year rule)

Inherited Traditional IRA and Inherited Roth IRA model an IRA you inherited as a beneficiary (post-SECURE Act, using the 2024 final regulations effective 2025+). They behave very differently from your own IRAs, and modeling one as a brokerage account (wrong tax treatment) or as your own IRA (wrong RMD age, wrongly aggregated) badly distorts the plan.

How the drawdown rules work

• No early-withdrawal penalty at any age - death-exception distributions are always penalty-free, so the withdrawal planner treats inherited money as a preferred early-retirement funding source (it has to come out anyway).
• No new contributions, ever - inherited accounts cannot be a Cash Flow Priority target and receive no surplus deposits.
• Inherited Traditional distributions are ordinary income - they interact with bracket-fill, ACA subsidies, and IRMAA like any other pre-tax withdrawal. Inherited Roth distributions are tax-free (the model assumes the 5-year holding period is met).
• Never aggregated with your own IRAs - each inherited account satisfies its own required distribution separately.
• QCD-eligible - a Qualified Charitable Distribution can come from an Inherited Traditional IRA once the beneficiary is 70½, and it counts toward that account's own required distribution.

An inheritance you expect to receive later

The When did (or will) you receive it? selector has two settings. Already inherited is the default: the account is in your name today, you enter the year the original owner died, and you enter its balance. Future inheritance models an IRA you expect to inherit in a later year - the balance is locked at $0 and the death-year field disappears, because the timing lives on a linked Inheritance event instead.

Use the Create linked Inheritance event button on the account to make the matching event, or pick the account from the Deposits into inherited IRA selector on an existing Inheritance event. The 10-year clock starts in the year that event fires, so changing the event's year moves the whole schedule with it. The amount is entered in today's dollars and inflated to the year it arrives, like every other income event.

A future-inheritance account with no linked event shows an amber warning on the account card, and the simulation refuses to run until you either link an event or switch the account back to Already inherited and enter a death year. An account that is simply unfinished — no name, no allocation, no owner — blocks Run too, and each such field gets its own row in the setup drawer's Needs attention section with a button that opens that account.

Out of scope in this version (enter the closest category instead): minor-child beneficiaries (stretch until 21, then 10-year), successor beneficiaries inheriting an already-inherited IRA, estates and non-qualifying trusts (5-year rule), deaths before 2020 grandfathered into the old stretch rules, and state-level differences in how inherited distributions are taxed.