Thank you for your question,
Unfortunately, a chair is not an eligible expense that you can deduct as an employment expense for working from home due to COVID.
To claim expenses you paid for working from your home, you must meet all conditions that are mentioned on the CRA website Eligibility criteria.
Some expenses eligible to deduct are electricity, heat, water, utilities, home internet access fees (new for 2020), maintenance and minor repairs, and rent. (Commissioned employees can also claim some other expenses).
You can find information related to expenses you can claim here: Expenses you can claim.
