Question: My employees are currently working from home. How can I find out which of the expenses incurred by this are taxable please?

Answer passage (source: UK):
page_title: Guidance Check which expenses are taxable if your employee works from home due to coronavirus (COVID-19)
section_headers: Type of equipment, service or supply
section_content: Mobile phones and SIM cards (no restriction on private use)
If you provide a mobile phone and SIM card without a restriction on private
use, limited to one per employee, this is non-taxable.
Broadband
If your employee already pays for broadband, then no additional expenses can
be claimed.
If a broadband internet connection is needed to work from home and one was not
already available, then the broadband fee can be reimbursed by you and is non-
taxable.
In this case, the broadband is provided for business and any private use must
be limited.
Laptops, tablets, computers, and office supplies
If these are mainly used for business purposes and not significant private
use, these are non-taxable.
Reimbursing expenses for office equipment your employee has bought
If your employee needs to buy home office equipment to allow them to work from
home, they will need to discuss this with you in advance.
If you reimburse your employee the actual costs of the purchase, then this is
non-taxable provided there is no significant private use.
If you do not reimburse your employee, then they can claim tax relief for
these purchases on their tax return or P87 as long as the amount claimed is
incurred wholly, exclusively and necessarily in the performance of their
duties of employment.
Your employees will need to keep records of their purchase and claim for the
exact amount. For more information on the strict tests that need to be passed
in order to qualify for tax relief see the guidance on Employment
Income.
Additional expenses like electricity, heating or broadband
Payment or reimbursement to your employees of up to £4 a week (£6 a week from
6 April 2020) is non-taxable for the additional household expenses incurred
when your employee is working from home.
If the claim is above this amount, then your employee will need to:

check with you beforehand to see if you will make these payments
keep receipts

Employer provided loans
A salary advance or loan to help your employee at a time of hardship counts as
an employment-related loan.
Loans provided with a value less than £10,000 in a tax year are non-taxable.
Further information on loans.
Temporary accommodation
If your employee needs to self-isolate but cannot do so in their own home, you
can reimburse hotel expenses and subsistence costs, these are taxable.
Further information on accommodation expenses.
Employees using their own vehicle for business
You can pay approved mileage allowance payments of 45p per mile up to 10,000
miles (25p per mile thereafter) free of tax and National Insurance
contributions.
If you do not pay mileage allowance, your employee can claim tax relief
through their Personal Tax Account.
Further information on approved mileage allowance
payments.

Reviewer feedback on this answer:
This is a detailed article about what expenses can be considered taxable for work at home employees' employers.
gives adequate responses to set rules and structures in the work place.

Reviewer ratings:
Excellent
Acceptable

Answer passage (source: UK):
page_title: Guidance Check which expenses are taxable if your employee works from home due to coronavirus (COVID-19)
section_headers: How to report to HMRC
section_content: Taxable expenses or benefits
Any expenses or benefits which are related to coronavirus can be reported on
your PAYE Settlement Agreement.
This means you can settle tax and National Insurance contributions on any
expenses or benefits, even though the responsibility would usually be on your
employee, or on both you and your employee.
This applies to coronavirus related items only, for example, a new desk can go
onto the PAYE Settlement Agreement, but a new sofa cannot.
If you are currently payrolling benefits in
kind, you may continue to report expenses and
benefits through your payroll. You may also continue to report expenses and
benefits through P11D returns.
Non-taxable expenses or benefits
Do not report to HMRC.
Further information on non-taxable expenses or benefits for
employees.

Reviewer feedback on this answer:
This is acceptable as it talks about taxes but only mentions about virus related taxation rather than broad based.
This offers information about payroll taxes, but does have a link to information about taxable expenses.

Reviewer ratings:
Acceptable
Could be Improved

Answer passage (source: UK):
page_title: Guidance Check which expenses are taxable if your employee works from home due to coronavirus (COVID-19)
section_headers: Contact HMRC
section_content: Contact HMRC if you’re an employer and need
help and support on paying tax due to coronavirus.
Get help online
Use HMRC’s digital assistant
to find more information about the coronavirus support schemes.

Reviewer feedback on this answer:
This discusses employer taxes but does not address taxable expenses.
shows how to adequately  contact the employer or team

Reviewer ratings:
Bad
Excellent