Residual item or partial payment &2//&3 for fee &1 exists

What causes this issue?

Partial payments and residual items pertaining to a fee document should
be included in clearing.

System Response

Posting cancelled.

How to fix this error?

Select additional documents manually in one of the following ways:
From the open item screen by choosing <LS>Edit --> Select More</>.
On the next selection screen (Post Incoming Payments Select Open Items)
flag the document number, then, in the subsequent screen, enter the
document number(s) suggested in this message.
From the Post Incoming Payments Display Overview screen, click 'Choose
Open Items (F6)'.
On the next selection screen (Post Incoming Payments Select Open Items)
flag the document number, then, in the subsequent screen, enter the
document number(s) suggested in this message.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.