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.
Technic Panel Fairing #21 5L Small Smooth, Side BDark TanPart 11946Element 6593774 or 6352644×2
Technic Panel Fairing #22 5L Small Smooth, Side ADark TanPart 11947Element 6593776 or 6352663×2
Technic Special
4 pieces
Technic Ball Joint with Through Axle HoleBlackPart 53585Element 4286267×4
Projectiles / Launchers
3 pieces
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-Dark BluePart 15303Element 6296379 or 6065898×2
Bricks Curved
2 pieces
Brick Curved 4 x 1 Double, No StudsBlackPart 93273Element 4613153×2
Plates
2 pieces
Plate 1 x 1BlackPart 3024Element 3024261 spare in the box×2
Technic Beams
2 pieces
Technic Beam 1 x 2 Thick with Pin Hole and Axle HoleBlackPart 60483Element 6265091 or 6006140×2
Technic Beams Special
2 pieces
Technic Beam 3 x 0.5 Liftarm with Boss and Pin / CrankBlackPart 33299aElement 4156980×1
Technic Beam 5 x 5 x 2 Perpendicular Fork 3 FingersDark Bluish GrayPart 19086Element 6102645×1
Bars, Ladders and Fences
1 piece
Light Cover 1 x 1 Round with Internal Bar / Bionicle Barraki EyeTrans-Medium BluePart 58176Element 6006124 or 4506480×1
Bricks Sloped
1 piece
Brick Sloped 18° 2 x 1 x 2/3 with 4 Slots / GrateDark Bluish GrayPart 61409Element 4540386 or 4521185×1
Technic Bushes
1 piece
Technic Bush 1/2 Smooth with Axle Hole Semi-ReducedLight Bluish GrayPart 32123bElement 6271165 or 42115731 spare in the box×1
Tiles
1 piece
Tile 1 x 2 with GrooveDark Bluish GrayPart 3069bElement 4211052×1
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.