If you receive the error, the submission must include employees. When trying to submit a previous year update, it can be caused by submitting for an incorrect year, or historic pay frequency dates missing.
If you are submitting a PYU for 2020 onwards, raise a case with the support team for assistance in resolving the issue.
📌Note: HMRC will only accept a PYU submission for the tax year 2020 and onwards. For 2019 or earlier use HMRC's basic tools.