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Household & cash flow · plain-English guide

Model loans and extra repayments

Set a loan balance, interest rate, and payment plan, then explore paying it down before investing extra cash.

2 min readWorked example included
How to read itDebt repayment
Core relationshipclosing balance = opening balance + interest − payments, with extra principal limited to the amount owed

Conceptual illustration. The annual engine resolves the connected taxes and cash flows described below.

Start here

The basics

Add standalone debts for borrowing that is not already attached to a property. Choose a remaining term or a monthly payment. The plan calculates interest and principal inside each projected year.

To make extra payments, add a debt-paydown step in Cash flow and place it before the steps that would otherwise use the money.

Illustrative numbers

A payment that does not cover interest

Opening balance$10,000

Annual interest rate12%

First month’s interest$100

Monthly payment$80

After that first payment the balance is $10,020. Later interest is calculated on the remaining balance, so this payment does not pay the loan off.

Calculation transparency

How it works in MoneyWhatIf

  1. 01

    Term-based payments use monthly amortization, as mortgages do. A fixed payment is applied month by month; the final payment is limited to the payoff amount.

  2. 02

    Scheduled payments are household cash needs. The funding system can sell assets to meet them in a short year.

  3. 03

    Extra payments reduce the balance and future interest. A paydown after a full investment sweep may receive nothing; a mandatory paydown can cause another asset to be sold.

  4. 04

    Outstanding standalone debt reduces both net worth and liquid net worth. Disable a debt to compare a scenario without deleting its entered details.

Keep in mind

Model limits

Debt labels do not add lender-specific rules, promotional-rate schedules, fees, or loan-forgiveness programs.

Keep a property mortgage on its property card; also entering it as standalone debt counts the obligation twice.

This explanation documents the planning model. It is educational, not individualized tax, legal, Medicare, or investment advice.

Where it appears

Where to use it

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The words behind it

Related financial terms

Plain-English definitions, with 2026 figures and worked examples, from the financial terms glossary.

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