If you are an employee who receives a W-2 from your employer, none of your employee business expenses are deductible on a federal tax return due to the tax code changes in effect from 2018 thru 2025.
Sorry---W-2 employees cannot deduct job-related expenses on a federal return. Job-related expenses were eliminated as a federal deduction for W-2 employees by the tax laws that changed for 2018 and beyond. Your state tax laws might be different in AL, AR, CA, HI, MN, NY or PA.
If you live in a state that lets you deduct job-related expenses, the information will flow from your federal return to the state return, so enter it in Federal>Deductions and Credits>Employment Expenses>Job-Related Expenses
How do I determine how much I can deduct? The laptop is a few years old. (Note: I have not yet downloaded TurboTax, so I haven't looked at the form yet)
Assuming that you are eligible to deduct the cost of the older laptop that is used 100% for business, you would need to know the fair market value (FMV) of the laptop on the date that you converted it to business use. The FMV is the amount that will be deducted or depreciated on your return.
As you enter the information into that part of your return, the laptop will be entered as an Asset. You will need to know when it was purchased, how much it cost, when it was converted to business use, and the FMV on the date it was converted. TurboTax will then compare those values and determine which number to use as a deduction or for depreciation. The lower of the two values will be used.
You can search for a similar laptop for sale online to determine the best FMV showing what a willing buyer would pay for a similar machine.
To follow-up on the information shared by DoninGA and xmasbaby0, if you are an employee receiving a W-2, the FMV of the laptop will not be deductible on your Federal return. It may be deductible on your state return, depending on your state.
But, if you are a sole-proprietor filing a Schedule C, the laptop would be entered as an Asset for your Schedule C business.