You are trying to release billing document to accounting and you get KI280 error:
"Define a cost element category for account xxxx"
SAP S/4HANA Cloud
Reproducing the Issue
Release billing document to accounting
In S/4Hana Cloud, if you post a non statistical SD condition to the G/L account, it is automatically posted into profitabilty analysis. So it is ensured that the complete revenue is posted in profitability analysis. For the G/L account, a cost element category must be assigned. Otherwise releasing billing document to Financial Accounting is not possible.
This is standard design. You need to assign cost element category to the account.
KI 280, cost element category, billing, accounting, FI. , KBA , CO-OM-CEL-E , Postings , Problem