Intermediate
60 mins
Teacher/Student led
+80 XP
Pupils work on their own device

Tax Calculations with Formulas

In this lesson you will build a spreadsheet model to calculate estimated take-home pay from gross salary using a flat tax rate. This demonstrates how real tax calculators work while stressing that it is for practice only.

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    1 - Introduction ~5 mins

    Today you will

    • build a practice sheet that turns gross pay into take-home pay
    • use two formulas that update on their own
    • label the sheet as class practice only, not tax advice

    Illustration for IntroductionGross pay is your pay before deductions. Take-home pay is what is left.

    Warm-up

    Think of a wage for your project, like a Work Experience rate. How much of it do you think you would keep?

    2 - Key Concepts ~8 mins

    Gross pay is your pay before anything is taken off.

    Take-home pay, also called net pay, is what is left after deductions.

    A flat rate is one percentage taken off the whole gross figure. Real Irish tax has more rules, so today you use one rate.

    Not tax advice means your sheet is for class practice only, never for real pay.

    Example

    A Centra weekend job pays €14 an hour for 12 hours, which is €168 gross. At the 25% classroom rate, you keep €126.

    3 - Step-by-step Task ~15 mins

    You will add a new sheet called {{code:TakeHome_Pay}} to your VAT workbook, {{code:sm3_vat_calc}}. Follow the steps in the box below.

    With €2,400 gross and a 25% rate, you should get €600 tax and €1,800 take-home.

    The copy box shows what you will type:

    CellType this
    A1Take-home pay model (classroom only - not tax advice)
    A3Gross monthly pay (€)
    A4Flat tax rate (teaching only)
    A5Tax amount (€)
    A6Take-home pay (€)
    A8Real Irish take-home uses PAYE bands, tax credits, USC and PRSI. This sheet is a teaching model only.

    4 - Common Issues ~3 mins

    If something goes wrong

    • The tax is far too big. You probably typed 25 in {{cell:B4}}, so type 0.25 instead.
    • The results don't change. Type {{formula:=B3*B4}} into {{cell:B5}} and {{formula:=B3-B5}} into {{cell:B6}} again.
    • {{cell:B4}} no longer shows 25%. It got currency format by mistake, so set it back to Percentage.

    5 - Independent Practice ~20 mins

    Independent Practice

    Your goal: Put a real pay figure from your project into your sheet.
    Time: ~20 minutes
    Task: Open {{code:TakeHome_Pay}} in {{code:sm3_vat_calc}}, then:
    1. Change {{cell:B3}} to a gross figure from your project.
    2. Add a short label near the top that says what the figure is.
    3. In {{cell:A10}}, type where the figure came from, such as {{code:Source: WE hours x rate}}.
    4. Try two gross figures. Write each one and its take-home in columns C and D.
    5. In {{cell:A12}}, write one sentence on whether take-home covers one project cost.

    If you have no figure, use €2,200 a month or €14 an hour for 12 hours.

    Success criteria:
    • My gross figure comes from my project and has a label.
    • Tax and take-home change when I change the gross figure.
    • {{cell:A10}} has my source and {{cell:A12}} has my sentence.
    • The not-tax-advice note is still on the sheet.
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