COM23120 | Assessing: CTSA assessments: no determination required
From HM Revenue & Customs · COTAX Manual
You should set the ‘NDR’ (no determination required) signal in function RAMA (Record/Amend Assessment if:
there is no income for the AP
a revenue determination would contain only zeros
COTAX does not allow you to set the ‘NDR’ signal for any Accounting Period (AP) that has a payment recorded against it.
COTAX automatically deletes the signal for the AP if you later make a revenue determination.
See COM23012 for a list of functions to use in particular situations.