Average rate does not reflect the tax on the additional income.
Use the marginal rate (31.48% in this estimate) to calculate the additional tax on the next $1.00 income.
Another issue... If your estimated taxes on the additional income exceeded $3,000, you have to submit tax instalments or you may be subject to instalment interest penalties.
https://www.canada.ca/en/revenue-agency/services/payments-cra/individual-payments/income-tax-instalments/who-pays-instalments.html
Required tax instalments for individuals
Who has to pay
You may have to pay tax by instalments if your income does not have enough tax withheld or if you are self-employed, have rental or investment income, certain pension payments, or have income from more than one job.
Province or territory where you live
The province or territory where you live on December 31 determines your net tax owing for tax instalments.
All residents (except Quebec): Option 1 of 2
If your net tax owing is more than $3,000.
Net tax owing
Use the calculation chart for instalment payments for 2023 (PDF) to determine your estimated net tax owing and the total instalment amount you owe.
You have to pay your income tax by instalments for 2023 if both apply:
Net tax owing in 2023
If your net tax owing is more than $3,000, or $1,800 for Quebec.
Net tax owing in 2022 or 2021
If your net tax owing in either 2022 or 2021 is also more than $3,000, or $1,800 for Quebec.