A non-deductible expense is an expense that you can’t subtract from your income when you’re doing your Self Assessment tax return.

In simpler terms, you can’t use it to reduce your tax bill.

It’s not always obvious which expenses are deductible and which are non-deductible. The rule of thumb is that if the expense is not related to your self-employment or rental business, it is not considered allowable by HMRC.

Example of calculating the deductible amount of an expense:

• let’s say that you bought a laptop for your self-employed work
• but you’re also using it for your own personal use (social media, gaming, etc.) about 50% of the time
• the “personal use” is considered non-deductible (you can only claim 50% of the cost in your Self Assessment tax return).