How to Use the Quarterly Tax Estimator

Overview

What Does the Quarterly Tax Estimator Do?

The WorkersPool Quarterly Tax Estimator calculates how much to pay in each tax installment — and when — based on your prior year tax liability and projected current year income. It supports Canada (CRA quarterly, 3 methods), USA (IRS quarterly, 4 methods), UK (HMRC bi-annual Payment on Account), Australia (ATO quarterly PAYG Instalments) and New Zealand (IRD 3-instalment provisional tax).

For each country you get the installment due dates with exact calendar dates, your estimated payment amount for each installment, a comparison of all available calculation methods so you can choose the one that minimises your payments while staying safe from penalties, and a quarter-by-quarter set-aside guide showing how much to save each month.

Installment Schedules by Country

When Installments Are Due

Country	Due Dates	Threshold	Methods Available
Canada (CRA)	Mar 15, Jun 15, Sep 15, Dec 15	Net tax > $3,000 ($1,800 QC)	No-calculation, Prior year, Current year
USA (IRS)	Apr 15, Jun 16, Sep 15, Jan 15	Expect to owe > $1,000	100% prior year, 90% current year, Annualised
UK (HMRC)	Jan 31, Jul 31	Self Assessment bill > £1,000	Payment on Account (50% each)
Australia (ATO)	Oct, Feb, Apr, Jul (varies)	Instalment income > AUD $4,000	PAYG Instalment amount or rate method
New Zealand (IRD)	Aug 28, Jan 15, May 7	Residual income tax > NZD $5,000	Standard, Estimation, Ratio methods

Instructions

Step-by-Step Instructions

Select your countryChoose from Canada, USA, UK, Australia, New Zealand or Other. The tool adjusts all due dates, thresholds and methods to your country.
Enter your prior year net tax owingThis is your total income tax plus CPP/SE tax from last year's return — the final amount owing after all credits and withholding. In Canada, find it on Line 48500 of your T1. In the USA, it is your total tax from Form 1040. This is the primary input for all prior-year-based methods.
Enter two years ago tax (Canada only — optional)The CRA no-calculation method uses the average of the two most recent tax years. If you enter this figure, the tool can calculate your exact no-calculation installment amounts — the amounts CRA would put on your official installment reminders.
Enter your projected current year income by quarterFor each quarter, enter your estimated net self-employment income. These are used for the current-year method calculation — comparing it to prior-year methods helps you choose the lower payment option.
Enter your estimated tax rateYour combined effective tax rate on net self-employment income. Use the Self-Employment Tax Calculator to determine your rate — it accounts for income tax and social contributions for your country and province.
Click Calculate Installment PlanAll methods are calculated and shown side by side. Your payment schedule appears with exact dates and amounts. The quarter-by-quarter set-aside guide shows how much to save each month to have the installment ready when due.

Choosing the Right Method — Canada

Canada: Which CRA Method Should I Use?

Method	How It Works	Best When
No-Calculation	CRA tells you the amount based on your 2-year history. Safest — no math required.	Income is stable year-over-year. You want to follow CRA's reminders exactly.
Prior Year	Pay 25% of last year's total tax each quarter.	Income is rising — prior year is lower than current year, so you pay less throughout the year and a balance at filing.
Current Year	Estimate current year tax and pay 25% each quarter.	Income dropped significantly — reduces installments now but requires accurate estimation. If you underestimate, interest applies.

Safe harbour rule: If your installments equal at least the prior year tax obligation, CRA will not charge interest even if your current year tax is higher. The prior year method is therefore the safest choice when income is growing.

Worked Example

Example: Maya Plans Her 2025 CRA Installments

Inputs

CountryCanada

Prior Year (2024) Net Tax Owing$18,400

Two Years Ago (2023) Net Tax$15,200

2025 Projected Net Income$98,000 (all 4 quarters entered)

Effective Tax Rate32%

Method Comparison

No-Calculation Method (each quarter)~$4,200 × 4 = $16,800/yr

Prior Year Method (each quarter)$4,600 × 4 = $18,400/yr ← Safest

Current Year Method (each quarter)~$7,840 × 4 = $31,360/yr

Maya's ChoicePrior Year — lower than current year, safe from interest

Due DatesMar 15, Jun 15, Sep 15, Dec 15 2025

Monthly Set-Aside$1,533/month to have each $4,600 ready on time

Maya uses the prior year method — paying $4,600 per quarter protects her from interest even though her income grew significantly. She will owe a balance at filing (approximately $12,960) but pays no penalties. She sets a calendar reminder for each due date and saves $1,533/month into her tax account.

Disclaimer

Important Disclaimer

The Quarterly Tax Estimator provides rough installment estimates for planning purposes only — not tax advice. Actual required installment amounts depend on your tax authority's specific calculation method and your confirmed prior year tax liability. Underpaying installments results in non-deductible interest charges. Always verify with your tax authority or a qualified tax professional before making payments. WorkersPool accepts no liability for tax or financial decisions based on this tool.

FAQ

Frequently Asked Questions

What happens if I miss an installment payment?

Missing or underpaying an installment results in compound daily interest on the shortfall — not a separate penalty in most countries. In Canada, CRA charges interest at their prescribed rate (currently 8–10% annualised), compounded daily. This interest is non-deductible — you cannot write it off as a business expense. The cost of missing installments adds up quickly; setting calendar reminders and automating transfers to your tax account eliminates the risk entirely.

What if my income is very different from last year?

If income dropped significantly, the current year method lets you pay lower installments based on what you actually expect to earn — but you are responsible for the accuracy of your estimate. If you underestimate and your actual tax is higher, interest applies on the shortfall. If income rose significantly, the prior year method is safer — you pay based on last year's lower tax, accept a larger balance at filing, but avoid any interest risk.

Do installment payments earn interest if I overpay?

No — overpaid installments are credited against your final tax bill and any excess is refunded when you file. CRA does not pay interest on overpayments in the same way it charges interest on underpayments. This asymmetry is why many accountants recommend paying slightly more than required in the prior year method — the cost of overpaying is low (opportunity cost only); the cost of underpaying is real non-deductible interest.

I am in my first year of self-employment — do I need to pay installments?

Typically no — the CRA threshold test requires the net tax owing to exceed $3,000 for the current year AND either of the two prior years. In your first year, the prior year test is not met. However, you will still owe all taxes when you file your first return — often a large, unexpected bill. Even in year one, set aside the correct percentage of every payment you receive into a separate savings account. You will not pay installments yet but you will owe a lump sum at filing.

Can I pay installments online?

Yes — and online payment is strongly recommended. In Canada, pay through CRA My Account, your bank's online bill payment (payee: CRA), or My Payment on the CRA website. In the USA, use IRS Direct Pay or EFTPS. In the UK, pay through HMRC's online portal. In Australia, use BPAY or the ATO's online payment facility. In New Zealand, pay through myIR. Online payment is instant, generates a reference number and eliminates the risk of a cheque being delayed or lost.

Official Sources

Installment Payment Portals

Pay installments directly through official channels:

Quarterly Tax Estimator — Help Guide