Rule out the usual hiding places first. If the piece really is gone, check the set piece by piece
and leave with the element ID LEGO asks for, or a link to buy the part.
Duplo Brick 2 x 2 x 1 1/2 with Curved TopWhitePart 11170Element 6217780×2
Duplo Brick 2 x 3 with Curved TopWhitePart 2302Element 6172232 or 6004947×4
Duplo Brick 2 x 4 Curved TopWhitePart 98223Element 6135522×3
Duplo Plate 2 x 8WhitePart 44524Element 4563575×4
Duplo Plate 4 x 8WhitePart 4672Element 6109109 or 6016280×2
Duplo Brick 2 x 2YellowPart 3437Element 4583546 or 343724×1
Duplo Brick 2 x 2 Slope 45°YellowPart 6474Element 4118928×2
Duplo Rear Spoiler 2 x 4 x 1 / 2 [Plain]YellowPart 89398Element 6601070×1
Duplo Trophy Cup with Number 1 in Shield - Closed Handles, Shallow NotchesYellowPart 5643Element 6498913×1
Tick each piece as you find it, or mark it missing.
When a piece really is missing
Ask LEGO
LEGO takes requests for pieces missing from a new set through its customer service site. The form asks for
the set number and each piece's element ID, the number printed beside the piece in the parts list at the back
of the instructions. This checker lists both.
Mark a piece missing and your list links it to an eBay search for that part, which also covers pieces from
older or second-hand sets.
Keep a record
Copy or download your missing list (the CSV opens in any spreadsheet), or print the whole checklist and tick
pieces off on paper. Your marks stay in this browser, so you can check a big set over several sittings.