In transfer pricing, a frequent “comparability adjustment” to (gross or operating) profits involving inventories is spurious. The OECD is wrong disseminating misconceived guidance about “working capital” adjustment that includes inventories. The inventory adjustment to profits is bogus because inventory is included in cost of goods sold (COGS); thus, the same inventory variable appears on both sides of the adjustment equation, making the proposed adjustment false. Follow at your peril: OECD, Comparability Adjustments (July 2010), ¶¶ 16-17: http://www.oecd.org/tax/transfer-pricing/45765353.pdf
The IRS has published similar argy-bargy: https://www.irs.gov/pub/irs-apa/study_guide_exhibit_d.pdf