Partnership Start-up - effect on Payment on Account

Hello, I prepare the cash-basis sole trader accounts for a niece. With effect from April 24/25 tax year she formed a partnership with another sole trader who had previously been providing services to her. The Partnership has not yet been registered with HMRC. The new partnership is effectively the continuation of my niece’s previous sole trader business. My questions: - When submitting the final 23/24 Sole Trader accounts to HMRC, should she state that she ceased trading on 5 April 24 even though the business continued as a partnership? In which case I assume there will be no Payment on Account for 24/25 due on 31 January 24? - Does HMRC consider the new partnership as a start-up for the first year with no POA being collected from the partners? - should she register the partnership with HMRC before submitting the final sole trader self assessment or can it wait until the October deadline? Thanks

Hi,
On the 2023 to 2024 tax return if the sole trader buisness has ceased she would enter the cessation date. As now in a partnership she would need to register the partnership using form SA400 and rergister as a partner using form SA401 if not already done. Details of how to register can be found online at:
Set up a business partnership
The payments on account are introduced based on the 2023 to 2024 Self Assessment tax return.
Details on payments on account at:
Understand your Self Assessment tax bill
Thank you.