Compare Two Monthly Household Budget Scenarios
Organise current and proposed monthly income and costs in separate budget scenarios, with supporting records, clear assumptions and a worked planning example.
To compare your current household budget with a proposed change, keep separate monthly columns for each scenario. Use existing statements and bills for the current plan, and record proposed amounts alongside their assumptions. Keep the original figures visible until you decide which version to use. The task here is to organise a comparison before replacing your working budget.
Govt.nz describes budgeting as a way to maintain control over your money and make use of what you have. [1]
The worksheet below is an optional recordkeeping approach. It separates the figures you currently use from figures you are considering, without treating a proposal as an established household cost or dependable income.
Define what the monthly comparison covers
Start by giving each scenario a descriptive name, such as “current household plan” and “proposed household plan”. Add the month you are planning for and the date you prepared the comparison. If the proposed change has no confirmed start month, write “start month unconfirmed” beside it.
Choose the same household scope for both columns. You might include all household income and costs, or only the amounts belonging to your own personal budget. Write that scope above the worksheet. Avoid comparing a whole-household current plan with a proposed column containing only your share.
For a comparison intended to show a household planning surplus, include the full set of income and cost lines within that scope. If you are only comparing selected costs, label the sheet as a partial comparison and leave out any claim about the household's overall surplus.
You could use these fields:
| Budget line | Current monthly plan | Proposed monthly plan | Record or assumption |
|---|---|---|---|
| Income included in the plan | Current amount | Proposed amount | Statement reference and income status |
| Housing | Current amount | Proposed amount | Existing bill or planned cost |
| Food and household purchases | Current amount | Proposed amount | Written category scope |
| Transport | Current amount | Proposed amount | Supporting record |
| Other household costs | Current amount | Proposed amount | Supporting records or assumptions |
| Total monthly costs | Current total | Proposed total | Included cost lines |
| Monthly planning surplus | Income minus costs | Income minus costs | Assumptions and unresolved items |
Adapt the headings to your records. Keep income outside the cost total, and keep the calculated surplus outside the expense rows.
Build the current monthly column
For the current column, use your existing monthly budget as the starting point. Beside each line, note the statement, bill or other record supporting it. A short reference such as a document name and statement period is enough for this worksheet; you do not need to copy every transaction into it.
Keep the column labelled as a plan. A planned amount and a recorded payment serve different purposes, so avoid silently replacing one with the other while assembling the comparison. If a bill differs from the amount in your working plan, leave a note identifying which figure you have used and why.
Retain any existing monthly planning averages with their calculation notes. Label them as averages rather than bills due in the planning month. A monthly average is a planning allocation, not money available before a payment falls due. Keep any due-date information with the supporting record.
Where an amount is uncertain, write down the uncertainty instead of leaving an unexplained blank. You could mark the line “amount awaiting confirmation” and put it on an unresolved list. If an essential figure is missing, label the total as incomplete rather than presenting it as the complete household cost total.
Record proposed changes separately
Work and Income says a household budget should reflect changes to income or costs, and that goals may also need revisiting. [2]
As an optional worksheet method, copy the current plan into the proposed column before editing individual lines. Change only the amounts involved in the proposal. Leave a short note beside each changed line explaining its basis, such as an existing bill, a planned cost or an amount still awaiting confirmation.
For a proposed move, for example, you could keep the existing housing amount in the current column and enter the proposed housing cost separately. Record other related planned costs on their own lines. Use the amounts supplied in your records.
Keep uncertain income clearly labelled. Do not treat a possible payment, extra work or one-off receipt as dependable monthly income. If you choose to include it in a conditional scenario, make that condition visible in the scenario name and beside the income line. Keep your current plan separate.
Use matching category definitions across both columns. If your food line includes household cleaning purchases, retain that same scope in the proposed version. If you want to change the category boundary, document the change and reorganise both columns before comparing their totals.
Read the monthly planning calculation
The worked example illustrates monthly income minus monthly costs under fixed hypothetical assumptions. It is an arithmetic reference for reading a scenario column, not evidence for any of your household figures.
Hypothetical cash-flow example
These invented figures demonstrate arithmetic, not typical incomes or recommended spending amounts. Assume take-home income and all planned costs stay the same each month. Costs include essentials, required debt payments and other planned spending. Start with no money set aside for this example; assume no interest, fees, withdrawals or unexpected costs.
| Item | Amount |
|---|---|
| Monthly take-home income | NZ$5,200 |
| Total monthly planned costs | NZ$4,850 |
| Monthly amount left: 5200 minus 4850 | NZ$350 |
| Amount set aside after 6 months: 350 times 6 | NZ$2,100 |
This total is possible only if the full amount left is set aside each month under these assumptions. It is not a forecast. If income falls or costs rise, recalculate before choosing an amount to set aside.
A monthly planning surplus does not show the cash available today or before a bill is due. Check the current balance and the dates and amounts of expected income and payments before setting money aside; keep money needed for bills available.
For your own worksheet, calculate each scenario separately. Subtract that column's total monthly costs from its monthly income. Describe a positive result as a planning surplus. Do not add the surplus back into the cost total as another expense.
The example assumes that all surplus is set aside each month. Your worksheet does not establish that this will happen. Its result depends on the income, costs and assumptions recorded in that particular column, including whether any figures remain unresolved.
A monthly planning surplus does not establish your bank balance on a particular date. That requires the starting balance and the dates and amounts of income and payments. Keep the monthly comparison separate from any decision about whether money is available before a bill is due.
Keep the comparison with its supporting records
You could save the comparison alongside the statements, bills and planned-cost notes used to prepare it. Give the worksheet a status such as “draft”, “awaiting information” or “selected plan”. Keep the scenario names visible when printing or sharing it.
Before selecting a version, review the unresolved list. Record whether each missing amount has been confirmed, remains uncertain or has been excluded from the comparison. State any exclusions beside the totals; do not silently treat unknown costs as zero.
If you adopt the proposed version, retain the comparison and mark which plan you selected. You may also choose a review reminder tied to an unresolved figure or your next monthly planning session. This is an organisational choice, not a required review frequency.
Frequently asked questions
Should both scenarios use the same month?
For this worksheet, use the same monthly planning period and household scope. If a proposal applies later, label it with its intended month and identify any assumptions needed to compare it with the current plan.
Can I compare only the cost that might change?
Yes. Label that sheet as a partial cost comparison. The difference between selected costs does not establish a whole-household surplus or money available to spend or save.
What if the proposed amount is still unknown?
Keep it on the unresolved list and label the proposed total as incomplete. You can retain the comparison while awaiting information, without replacing your current working plan.
This article is general information, not personal financial advice.
