Basis period reform profit spreading period

When a sole trader takes on a partner and a partnership is formed it is treated as a continuation of trade for tax purposes. If the sole trader has transition profits brought forward that have been spread over 5 years, is the change from sole trader to partnership treated as a continuation of trade and the profit spreading continues or is it treated as a cessation of the sole trader business and the remaining profits chargeable at the date of the partner being added?

Hi,
When a partnership is formed it changes the business's legal structure. Effectively, the sole trade ceases and the partnership begins. For details on reporting this please see thr following guidance:
Tell HMRC about a change to your business 
Assets that where used by the original sole trader that continues to be owned by them does not trigger a capital gain. Only if the asset is to change physical ownership to the other partners may trigger a capital gain based on the percentage of the asset ownership is being transferred. You can see guidance here:
PM272100 - Capital gains- introduction
Thank you.