---
title: "A sign error in a free trial's first order"
description: "A free trial's first order earns zero. A sheet that books it as minus the price charges the trial for the product twice, and a trial that pays back is rejected."
url: https://offersuite.io/articles/sign-error-in-a-free-trial
updated: 2026-10-13
---

# A sign error in a free trial's first order

A free trial's first order earns zero. A sheet that books it as minus the price charges the trial for the product twice, and a trial that pays back is rejected.

Spreadsheet mistake 9 of 9

## The mistake

A free trial's first order brings in nothing. Its margin is zero revenue minus the cost of the product, the pick and the label. That loss is the price of the trial.

In the sheet, the trial tab is a copy of a discount tab, where a discount cell is subtracted from the price. For the trial, someone enters the full price as the discount and also negates the price cell. First-order revenue comes out as minus the price instead of zero.

## A worked example

A bag of coffee at $40.00: the first bag free on a monthly subscription, 10% off after that, shipped free. The trial order costs $24.79 to fulfil and earns nothing, so it loses $24.79.

The sheet shows a first-order revenue of −$40.00 and a loss of $64.79.

Each renewal keeps $8.37. With 85.0% of subscribers taking each next order, the real loss is recovered at renewal 5. The sheet's loss is larger than the $47.43 a subscriber's renewals earn over a whole lifetime, so on the sheet the trial never pays back.

A free first bag, as the sheet books it and as the order goes

| Line | The sheet | The order |
| --- | --- | --- |
| First-order revenue | −$40.00 | $0.00 |
| First-order costs | −$24.79 | −$24.79 |
| First-order margin | −$64.79 | −$24.79 |
| Renewals to recover it, at 85.0% retention | never | 5 renewals |

The order's figures are computed by the margin engine in Offer Suite's own code, in whole cents. The sheet's are the same order with the mistake applied.

## What it does to the decision

The trial is rejected for a loss it doesn't have, and the team keeps a weaker intro offer. Set beside a percent-off intro, the trial is charged the product's price twice: once as revenue it didn't collect, and once more as a negative.

Sign errors survive because the result is plausible. A free trial is supposed to lose money on the first order, so a large loss draws no second look.

## What prevents it

Offer Suite holds no first-order revenue cell. The first charge is what the offer document says the customer pays, zero for a free trial, and [publish checks it on a real cart](https://offersuite.io/features/publish-and-verify) along with the price of every later billing cycle. Costs are amounts the margin engine subtracts in one place, and a price is never one of them.

To set a trial beside other intro offers on the same footing, the [subscription intro offer calculator](https://offersuite.io/calculators/subscription-intro-offer) runs each as a cohort with its own first-order margin, renewal margin and conversion.

A spreadsheet is still the right tool for some of this. Where it is, and where it stops: [Offer Suite vs a spreadsheet](https://offersuite.io/compare/spreadsheets).

## Where the numbers come from

The example is not a real brand's offer. The 85.0% retention rate is made up, and so is the trial: the sourced subscription takes 20% off its first order. Every other input is sourced below, or marked there as an assumption.

|  |  |
| --- | --- |
| Price | $40.00, a bag of coffee. Offer Suite's dev store catalog |
| Unit cost | $12.00. Offer Suite's dev store catalog |
| Refund reserve | 5%, Offer Suite's default assumption for consumables. NRF's all-category figure for online sales is 19.3%, but consumables are rarely returned; use your own rate. |
| Pick and pack | $3.20 per order and $0.48 for each extra item. [Fulfill.com, 3PL pricing benchmarks (The Fulfillment Advisor 2025 survey of 600+ warehouses), read 23 September 2026](https://www.fulfill.com/3pl-pricing) |
| Shipping label | USPS Ground Advantage, commercial, Zone 5, by weight rounded up to the pound: 1 lb $9.29 · 2 lb $10.50 · 3 lb $12.12 · 4 lb $13.89 · 5 lb $14.53. Packed weight is an assumption: 0.8 lb per unit. [USPS Notice 123, USPS Ground Advantage Commercial, Zone 5 (effective 4 October 2026), read 13 October 2026](https://pe.usps.com/text/dmm300/Notice123.htm) |
| Card fees | 2.9% + $0.30 per order: Shopify Payments' online rate for a standard card on the Basic plan in the United States. Higher plans pay a lower rate, and premium cards a higher one. [Shopify's pricing page for the United States, online standard card rates, read 12 October 2026](https://www.shopify.com/pricing) [Rates by plan and country](https://offersuite.io/fees/shopify-payments/united-states) |

## Related

- [Articles **Spreadsheet mistakes that misprice offers** Nine mistakes that turn up in offer spreadsheets, each worked on a sourced order: what the sheet shows, what the order earns, and what prevents the error.](https://offersuite.io/articles)
- [Calculator **Subscription intro offer calculator** Subscribe and save, a discount on the first order, a free trial or a free product: each as a cohort of subscribers with the same costs, ranked on profit per visitor after acquisition.](https://offersuite.io/calculators/subscription-intro-offer)
- [Calculator **Subscription payback calculator: CAC and churn** How much a subscriber's first order loses against what you paid to acquire them, how many renewals it takes to earn that back with churn, and in which month.](https://offersuite.io/calculators/subscription-payback)
- [Comparison **Offer profit in a spreadsheet vs Offer Suite** Where a spreadsheet is the right tool for offer profit, and where it breaks: costs that change, renewals, refunds, and a price that has to match checkout.](https://offersuite.io/compare/spreadsheets)
- [Article **Why your 3-pack costs almost the same to ship** A shipping label is priced in whole-pound steps and a warehouse charges little for an extra item, so a three-pack ships for barely more than one unit.](https://offersuite.io/articles/why-a-3-pack-costs-almost-the-same-to-ship)
- [Feature **Publish and verify on a real Shopify cart** Publishing writes the offer to Shopify, builds a real cart for every visible option and goes live only if each one charges what the offer promises.](https://offersuite.io/features/publish-and-verify)