> ## Documentation Index
> Fetch the complete documentation index at: https://docs.hazel.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Solver assumptions

> Your firm's planning policy in one place: probability, fees and taxes, and decumulation strategy.

Your firm has a house view on how much cash a retiree holds, when spending gets trimmed, and how far to push Roth conversions. **Solver assumptions** are where you write it down once, so every plan runs on it rather than on whoever built it.

They live in **Settings → Planning → Solver assumptions**, a firm owner's screen. There is no Save button: edits save when you move off a field, and an indicator reads "Saving…" and then "Saved". Firm owners can also open the screen from the **Planning settings** gear in the top bar of a plan open in its chat.

A small tag beside each field name reads **Overridable per persona** or **Set Firm-wide**, the field's scope.

## Probability & simulation

* **Success threshold** (Overridable per persona). The probability of success a plan solves toward, shipped at 90%. Below it, the plan is flagged.
* **Monte Carlo simulations** (Set Firm-wide). How many market paths each projection models. More are more precise and slower. The shipped value is 1,000.

Raise the success threshold and plans turn more conservative: more saving, later retirement dates, lower sustainable spending. It is the bar the math must clear, not a ceiling on what a plan may display, which is a separate firm setting in the [Assumptions reference](/guides/financial-planning/assumptions/reference).

## Fees & taxes

* **Advisory fee** (Set Firm-wide). Annual fee drag applied to assets under management in every projection.
* **Terminal heir tax rate** (Set Firm-wide). The rate heirs are assumed to pay on inherited pre-tax balances, used to value the after-tax estate.

## Decumulation strategy

Four fields, three of them free text, all overridable per persona.

<AccordionGroup>
  <Accordion title="Default reserve length">
    A slider, in years: how much retirement spending the plan carves into safe assets, so a client never sells equities into a down market. It ships at three years.
  </Accordion>

  <Accordion title="Reserve refill policy">
    The text box under the reserve-length slider, with no heading of its own, says what the reserve holds and when it is topped back up. What ships:

    "Hold the reserve in cash, T-bills, and short-duration bonds. Refill it from equities in years the portfolio finished up."
  </Accordion>

  <Accordion title="Retirement withdrawal guardrails">
    Your spending policy in retirement, written as rules that adjust as markets move. What ships:

    "Use Guyton-Klinger guardrails: trim spending 10% when the withdrawal rate drifts 20% above its initial target, and raise it 10% when it falls 20% below. Skip the inflation raise in any year the portfolio finished down."

    Three suggestion chips sit under the box: **Savings rate**, **Debt-free date**, and **Simple assumptions**. Each appends a sentence to whatever the box already holds, so clear the box first to use a chip's wording alone.

    This is spending policy. Rules Hazel must never break belong in [Guardrails](/guides/financial-planning/assumptions/guardrails).
  </Accordion>

  <Accordion title="Default Roth conversion strategy">
    Six choices, one at a time, setting the default ceiling for annual conversions. The chips read exactly:

    * **Stop under first IRMAA tier**
    * **Cap at ACA-subsidy MAGI**
    * **Drive off the heir's bracket**
    * **Fill to top of 24% bracket**, fixed at 24 percent rather than a bracket you pick
    * **Low-income years only**
    * **No default**

    The shipped choice is **Stop under first IRMAA tier**, elaborated in the box below it: "Convert each year up to just under the first IRMAA tier, so the client avoids a higher Medicare Part B/D premium."

    Hazel honors that box over the chip where the two disagree, so a house rule like filling the 22 percent bracket for ages 60 to 72 goes there, with whichever chip is closest.
  </Accordion>
</AccordionGroup>

## The three layers

Every value a plan uses comes from one of three layers:

* **Firm.** Everything on this screen.
* **Persona.** The matched Client persona's own values, for the fields tagged **Overridable per persona**. A persona carries only what it changes and inherits the rest, so it does not go stale when you edit a firm number.
* **This plan.** One household's plan, changed in that plan's **Plan settings** panel in the chat view.

The three personas Hazel installs already use that layer, with their own success thresholds, reserve lengths, Roth strategies and withdrawal wording. A persona copied from another brings those values along; one started from the **Base template** inherits everything.

## Changing one plan

<Steps>
  <Step title="Open Plan settings">
    Open the plan in its chat, and the sliders icon labeled **Plan settings** in the top bar opens a panel on the right. A household's **Financial Planning** tab has no sliders icon, so press **Open chat** first.
  </Step>

  <Step title="Read where each value came from">
    Every row carries a chip: **Firm**, **Persona** with the persona's name, or **This plan**. **Withdrawal guardrails** appears read-only, naming the layer that supplied the wording.
  </Step>

  <Step title="Change what you need">
    Three solver fields are adjustable per plan: **Success threshold**, **Reserve length**, and **Roth conversion strategy**, alongside any market row your firm has hand-edited. A value outside the allowed range is refused with the range named, not quietly rounded.

    The advisory fee, terminal heir tax rate, and simulation count never leave the firm, so the panel leaves them out.
  </Step>

  <Step title="Apply and replan">
    Nothing changes until you press **Apply and replan** in the panel's footer. A reset arrow on a changed row restores the inherited value, and **Discard changes** drops everything staged. The button stays unavailable until you change something, and while Hazel is mid-turn in that chat. Applying posts a short message in the chat.
  </Step>
</Steps>

<Note>
  The plan's **Appendix** carries the same provenance: every row under **Solver assumptions** in the **Applied settings** block is tagged **Firm**, **Persona**, or **This plan**. See [Where numbers come from](/guides/financial-planning/your-data/where-numbers-come-from).
</Note>

## Where to go next

* [Market assumptions](/guides/financial-planning/assumptions/market-assumptions): returns, volatility, inflation, taxes.
* [Guardrails](/guides/financial-planning/assumptions/guardrails): the rules nothing overrides.
* [Assumptions reference](/guides/financial-planning/assumptions/reference): every shipped default.
* [Client personas](/guides/financial-planning/settings/personas/overview): how a household gets matched.