Illumina's 19% Drop Puts Tariff Accounting in Focus

Illumina's 18.6% share-price drop on October 30 looked surprising because the company had just raised its full-year outlook. The explanation begins with an unusual tariff-refund accounting effect that made reported revenue and profitability move in opposite directions.

Reported third-quarter revenue was $1.129 billion, up 4.2% from $1.084 billion a year earlier but below the roughly $1.15 billion analyst estimate cited by Trefis. Excluding tariff-refund effects, Illumina reported $1.166 billion of revenue. That figure exceeded the cited estimate, but it is not interchangeable with reported revenue because the adjustment removes credits that the company expects to return to customers.

Illumina recognized a $79 million benefit as a reduction to cost of revenue for expected refunds of tariffs imposed under the International Emergency Economic Powers Act. At the same time, it reduced revenue by $37 million for the portion expected to be credited to customers. By September 27, the company had received $32 million of refunds, recorded a $47 million receivable for amounts still expected, and booked a $37 million liability for customer credits.

Those entries lifted reported margins while reducing reported sales. GAAP operating margin was 27.0%, and non-GAAP operating margin was 28.8%. Excluding the tariff-refund effects, non-GAAP operating margin was 25.0%. GAAP diluted earnings were $1.43 per share, while non-GAAP diluted earnings excluding the refunds were $1.44. Comparing the measures without the reconciliation would give a misleading picture of the quarter.

The operating business still delivered evidence of growth. Management said healthy clinical demand and more than 80 NovaSeq X placements supported results above its own guidance. The larger installed base should create recurring demand for sequencing consumables, but the outlook is uneven: Illumina expects clinical consumables to grow in the mid-teens in 2026 while research and applied consumables decline by the mid-to-high single digits.

Management raised its 2026 revenue forecast to $4.64 billion to $4.66 billion from $4.60 billion to $4.64 billion. It also lifted non-GAAP diluted earnings guidance, excluding tariff refunds, to $5.40 to $5.45 from $5.30 to $5.40. Fourth-quarter revenue is expected to be $1.22 billion to $1.24 billion, and management plans to issue its 2027 outlook with February results.

The selloff was much larger than the broader market move. Illumina fell from $290.06 on October 29 to $235.99 on October 30, while the S&P 500 declined 1.8% and the health-care ETF XLV rose 0.5%, according to Trefis. That gap suggests investors focused on the quality and composition of the quarter, not merely the market backdrop.

For the next report, the key question is whether NovaSeq X placements and clinical consumables can convert into reported revenue growth without one-time accounting effects obscuring the comparison.