SolvedPM147000 | Filing date for partnership return
From HM Revenue & Customs · Partnership Manual
The filing date for the SA 800 tax return (the partnership tax return) is usually 31 October for paper returns and 31 January for online returns. The filing date may be later if the return was issued late; the notice to file will always allow at least three months for a return to be submitted.
From 12 February 2019 where a voluntary partnership return is made and delivered to HMRC a notice to file a partnership return is treated as being given to the person who made and delivered the partnership return on the date it was received by HMRC. This date fixes the filing date of the return.
The presence of a company as a partner may affect the filing date of the partnership return. In such cases, the return must be issued manually and show a non-standard filing date.