The de minimis safe harbor is an annual tax election letting a business deduct low-cost tangible property immediately instead of depreciating it — up to $2,500 per invoice or item for a taxpayer with no applicable financial statement.
A $600 shock or $900 wheel set is what this is for. Under the IRS tangible property final regulations, a taxpayer without an applicable financial statement — nearly every racer — “may use the safe harbor to deduct amounts up to $2,500 ($500 prior to Jan. 1, 2016) per invoice or item”; with an AFS it’s $5,000. IRS ties $2,500 to Notice 2015-82; check current-year instructions. The written-policy trap runs backwards from the usual telling: writing is required only if you have an AFS. Without one you need “a consistent accounting procedure or policy existing at the beginning of the taxable year.” Elect by attaching a “Section 1.263(a)-1(f)” statement to a timely filed return. General education, not tax advice.
Getting the threshold and the election right turns a shelf full of $600 parts into this year's deduction instead of a depreciation schedule you're still tracking after the parts are junk.