There is no $400 credit. The Canada Revenue Agency (CRA) is allowing taxpayers who worked from home during the Covid-19 situation to deduct up to $400 from their income to compensate for expenses. This deduction reduces your taxable income, which may mean a reduction in the amount of taxes you need to pay.
This TurboTax FAQ tells you how to claim this deduction in TurboTax Online: Where do I claim my employment expenses in TurboTax Online?
Once you have filled in the Employment Expenses part of the return, you can see your deduction in TurboTax Online by looking at your Detailed Tax Summary or by downloading/printing a copy of your return. It appears on Line 22900 - Other employment expenses on the T1 General, in the Net Income section.
Please see the following TurboTax FAQs for instructions:
How can I see a detailed summary of my return in the online edition of TurboTax?
How do I print/save a copy of my return in TurboTax Online?
Thank you for choosing TurboTax.