Skip to content
Schedule C
Schedule C

Schedule CProfit or Loss From Business (Sole Proprietorship)

34 — Change in Determining Quantities, Costs, or Valuations Updated for tax year 2025

Does this apply to you?

  • You carry inventory and completed Part III last year
  • You changed your inventory counting method (physical count vs. perpetual system)
  • You switched how you assign costs to inventory (FIFO, LIFO, specific identification)
  • You changed your valuation method on line 33

Easy to overlook

Answering “yes” triggers an attachment requirement If you check “yes,” the IRS expects a written explanation attached to your return describing exactly what changed. Filing without the attachment can delay processing or prompt a follow-up letter. The explanation does not need to be long — a sentence or two describing the old method, the new method, and the reason for the change is sufficient. 1 IRS Schedule C instructions — Part III, Line 34

Some changes require Form 3115 Certain changes in accounting method — such as switching from FIFO to LIFO or changing your overall inventory valuation method — require filing Form 3115 in addition to checking “yes” here. A simple attachment is not enough for these changes. Consult the Form 3115 instructions to determine whether your change qualifies for an automatic change or requires advance IRS consent. 2 IRS Publication 334 — Tax Guide for Small Business

Watch out for this

Checking “yes” when you merely corrected a prior-year error rather than making a deliberate method change. Fixing a counting mistake or correcting a math error in your inventory valuation is not a change in method — it is an error correction. Only check “yes” if you intentionally adopted a different approach.

Footnotes

  1. IRS Schedule C (Form 1040) Instructions, Part III, Line 34. https://www.irs.gov/instructions/i1040sc

  2. IRS Publication 334, Tax Guide for Small Business. https://www.irs.gov/pub/irs-pdf/p334.pdf

Back to top