If the cardnumber doesn't exist, applying the koc file will still report success. - Upload .koc file, don't apply directly, but add to queue. - Take a look at the queue - verify cardnumbers shows in red and is not linked (not found) - Apply payment anyway - verify it reports "Success." The logs show: [Sun Aug 14 23:05:43.150296 2016] [cgi:error] [pid 18058] [client 127.0.0.1:43714] AH01215: [Sun Aug 14 23:05:43 2016] process.pl: DBD::mysql::st execute failed: Column 'borrowernumber' cannot be null [for Statement "INSERT INTO accountlines, referer: http://localhost:8080/cgi-bin/koha/offline_circ/list.pl [Sun Aug 14 23:05:43.150512 2016] [cgi:error] [pid 18058] [client 127.0.0.1:43714] AH01215: [Sun Aug 14 23:05:43 2016] process.pl: (borrowernumber, accountno,date,amount,description,accounttype,amountoutstanding,manager_id, note), referer: http://localhost:8080/cgi-bin/koha/offline_circ/list.pl [Sun Aug 14 23:05:43.150848 2016] [cgi:error] [pid 18058] [client 127.0.0.1:43714] AH01215: [Sun Aug 14 23:05:43 2016] process.pl: VALUES (?,?,now(),?,'',?,?,?,?)" with ParamValues: 0=undef, 1=1, 2=-1.05, 3='Pay', 4=-1.05, 5="1", 6=''] at /home/katrin/kohaclone/C4/Accounts.pm line 157., referer: http://localhost:8080/cgi-bin/koha/offline_circ/list.pl