Hi Sam,
The Self Assessment Manual at SAM70050 outlines the customer support we can provide with this type of enquiry.
The section ‘Your Charter’ confirms that we can of course direct customers to the relevant guidance, but we can't provide support with the calculation of specific business profits.
The Business Income Manual BIM81340 covers partners with trade profits and a rental business.
You may find example 25 particularly helpful.
BIM81340 - Transitional rules: partners with continuing notional business
Thank you.