SA103 or SA105

If I have income from both renting a property and trading (flipping) a property do I need to complete both supplementary pages of the self assessment tax return? If so, are losses from one transferrable to the other. For example, if there is a £20,000 profit from trading a property but a £4,000 loss from the rental business would I pay tax on £16,000?

Hi,
Thanks for your question.
I would advise that if Self-Assessment criteria is met on rental business profits, as well as sale of properties within your Self-Employment business, then both the SA105 UK Property and SA103 Self-Employment supplementary pages must be completed.
I must also advise that Capital Gains may apply upon sale of property.
Guidance can be found here: Tax when you sell property
If these conditions have been met and a profit exceeding your Annual Exemption Allowance occurs, then you would also be obligated to complete the SA108 Capital Gains supplementary page in addition.
Thank you.

Thank you for your reply. Can losses be transferred over? I believe losses from trading can be offset against rental income but not vice versa as in my example above. Is that correct?

Hi Danielle,
Yes, you are correct that you can claim losses from Self-Employment against your general income along as you are self-employed as a trade not as a hobby.  
You cannot use losses from property income against your general income.  
The guidance is here:
PIM4210 - Losses: setting losses against future profits.
HS227 Losses (2022).
Thank you.