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.
Launcher, Brick Special 1 x 4 Spring Shooter with Light Bluish Gray TopDark Bluish GrayPart 15400Element 6324200 or 6048898×1
Projectile, Spring Shooter Ammunition 8L BarTrans-RedPart 15303Element 6287550 or 6054526×2
Bars, Ladders and Fences
2 pieces
Bar 1L with Clip [Cut Edges and One Side Hole] [Gap in Clip]BlackPart 48729bElement 6278152 or 60373471 spare in the box×2
Technic Beams
2 pieces
Technic Beam 1 x 2 ThinBlackPart 41677Element 6338428 or 4167726×1
Technic Beam 1 x 3 ThickRedPart 32523Element 4153718×1
Tiles Special
2 pieces
Tile Special Round 1 x 1 with Hollow BarBlackPart 20482Element 6186675 or 61679331 spare in the box×2
Bricks Sloped
1 piece
Brick Sloped 30° 1 x 1 x 2/3 (Cheese Slope)Dark BrownPart 54200Element 6259071 or 60330141 spare in the box×1
Plates Special
1 piece
Plate Special 2 x 2 with 2 PinsDark Bluish GrayPart 15092Element 6284702 or 6066952×1
Pneumatics
1 piece
Pneumatic T-Piece (T Bar) [New Style]Pearl GoldPart 4697bElement 6452472 or 61679301 spare in the box×1
Technic Beams Special
1 piece
Technic Beam 1 x 3 with Ball Joint in MiddleDark Bluish GrayPart 98577Element 6001085×1
Technic Bushes
1 piece
Technic BushLight Bluish GrayPart 3713Element 6275844 or 62718171 spare in the box×1
Tiles
1 piece
Tile 1 x 3Dark BrownPart 63864Element 6167928×1
Transportation - Land
1 piece
Wheel Arch, Mudguard 4 x 2 1/2 x 2 with 2 x 2 PlateBlackPart 50745Element 4260488×1
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.