What happens to past orders when you change a cost in Shopify

The rule

Shopify’s profit reports are built on the cost recorded at the moment an item was sold. The help center puts it this way: profit is reported only for products and variants that had cost recorded at the time they were sold. It also notes that cost per item is static, so the data in profit reports is only relevant to a specific point in time.

Three situations follow from that rule.

1. You change a cost that was already there

New sales use the new cost. Shopify’s documentation does not state in so many words what happens to the figures for earlier sales, but “recorded at the time they were sold” describes a value captured with the sale. Reports from merchants in Shopify’s community are not all consistent on this, so if a restated history would matter to you, change one variant and compare a past period’s report before and after.

Either way, the product itself keeps no trace of the old value. If you need to know what the cost was last quarter, you need your own record.

2. You add a cost where there was none

Sales made while the variant had no cost are not counted as pure profit. They are excluded: the finance summary shows them separately as net sales without cost recorded, and Shopify says this is why net sales in sales reports and in profit reports can differ. Shopify documents no way to backfill a cost onto those sales.

So the cost of a missing cost is permanent for the period it was missing. That is the argument for finding empty costs on a schedule and not at year end.

3. You entered a wrong cost and sold with it

The sales carry the wrong cost. Fix the field so future sales are right, then correct the period where it matters, which is your accounts:

• work out units sold in the affected period, from a sales by variant report;
• multiply by the difference between the wrong and right cost;
• post that adjustment to cost of goods sold with your accountant.

What Shopify suggests

Because the field is static, Shopify lists three options for profit reporting that follows cost over time: run financial reports in an ERP or accounting system, use a reporting app, or calculate costs and profit manually.

Keeping the record yourself

Whichever you choose, the input is the same: for each variant, what it cost and from what date. Cogsy keeps that as a dated cost history, including costs changed directly in the Shopify admin, which it records as they happen.