GlossaryUpdated June 3, 2026 · Reviewed by Peasy Team

FIFO

FIFO (first in, first out) is an inventory costing method where the oldest stock is assumed to be sold or used first. In Peasy, FIFO is the oldest-cost-first model used for lot-aware costing and inventory valuation.

How It Works in Peasy

  • When you receive inventory, Peasy records the cost per unit for that batch, so every lot carries its own cost basis — no blended average
  • Shopify orders can apply FIFO automatically: enable Auto-assign lot IDs in your Shopify connection settings and Peasy picks the oldest available lot first, splitting across lots when one runs short
  • Regular sales orders don't auto-assign lots — you choose the lot on each line yourself. Whichever lot you pick, that lot's actual recorded cost is what flows into COGS, so choosing the oldest lot gives you true first-in-first-out costing
  • When a line has no lot assigned, Peasy falls back to the most recent production or receiving cost, then the template cost — this fallback is "latest cost," not an oldest-first lookup
  • Inventory History records the cost captured at each transaction, so you can audit which lot's cost was applied

Why It Matters

FIFO gives you an accurate, consistent way to value inventory and calculate margins, because each lot keeps the real cost it was received at instead of a standard or blended number. For Shopify orders you can let Peasy apply oldest-first automatically; for other orders you stay in control of which lot — and therefore which cost — each line uses.

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