When importing a new record and matching the bib and 'replacing' the item, Koha matches/overlays items on either barcode or itemnumber in the 952 $p or $9. However, it does not require that the item being overlaid be tied to the bibliographic record being matched in the import process. Example: Bib record 1: =LDR 01867cgm a2200433 a 4500 =020 \\$a1564589161 =245 00$aDog$h[videorecording] /$cBBC Wildvision ; BBC Lionheart Television and Dorling Kindersley Vision in association with Oregon Public Broadcasting ; =999 \\$c39742$d39742 =952 \\$aMAIN$bMAIN$cJVI$oJVID 636.7 Jol$pTVSN5$yVHS$93600 Bib record 2: =LDR 00925cam a22002775a 4500 =020 \\$a0716617471 (hbk.) =100 1\$aMorley, Christine. =245 00$aDog /$cChristine Morleyand Carole Orbell ; illustrations by Brita Granström. =999 \\$c35238$d35238 =952 \\$936713$aMAIN$bMAIN$cJVI$oJuv Mor$pBAR1$yVHS$95000 If you import the following record and use a 020$a matching rule you will match on bib #1, but overlay the item on bib #2. Koha gives no warning but simply overlays. =LDR 01867cgm a2200433 a 4500 =020 \\$a1564589161 =245 00$aDog$h[videorecording] /$cBBC Wildvision ; BBC Lionheart Television and Dorling Kindersley Vision in association with Oregon Public Broadcasting ; =999 \\$c39742$d39742 =952 \\$aEAST$bEAST$oJVID 636.7 Jol$pBAR1$yVHS or use the following item tag matching on the itemnumber =952 \\$aEAST$bEAST$oJVID 636.7 Jol$p57890000012345$yVHS$95000 This could be a problem particularly with libraries using an acquisitions process where items must be overlaid with new information. Koha should check to see that bib overlaid belongs to the bib that was matched before overlaying. Right now there is no indication that the overlay took place on a second bibliographic record.