Who this guide is for
Shopify merchants and buyers who make large upfront inventory commitments - particularly in apparel, footwear, and seasonal goods - and want a financial framework to govern their buying decisions rather than relying on gut feel.
The challenges of scale
Without an OTB framework, buyers routinely commit to more inventory than their sales plan and cash position can support - creating overstock, margin compression, and liquidity crises.
Shopify's native tools provide no OTB planner, no purchasing budget, and no mechanism to track remaining buying capacity against a plan.
Most content on OTB planning focuses on traditional retail department stores - the Shopify-specific implementation is rarely explained.
Forecasts and purchasing decisions live in separate spreadsheets; there is no unified view showing how much you've already committed and how much room remains.
Buyers often discover they've over-committed only when the cash flow statement reveals a problem - at which point it's too late to cancel or reschedule POs.
Fundamental concepts
Open-to-Buy (OTB)
A financial planning metric that determines how much merchandise a buyer can purchase in a given period without over-investing in inventory. It balances planned sales, planned inventory levels, markdowns, and already-committed on-order inventory.
Formula
OTB = Planned Sales + Planned End-of-Month Inventory + Planned Markdowns – Beginning-of-Month Inventory – On-Order InventoryExample: Planned sales: $100K. Planned EOM inventory: $60K. Planned markdowns: $8K. BOM inventory: $55K. On-order: $35K. OTB = $100K + $60K + $8K – $55K – $35K = $78K available to spend this month.
Planned Sales
The forward-looking sales forecast for the planning period, expressed in retail value. The most important input to OTB - if planned sales are wrong, the entire budget will be off.
Formula
Planned Sales = Last Year Sales × (1 + Planned % Increase) × Seasonal IndexExample: Last year November sales: $85K. Planned increase: +12%. Seasonal index already baked in. Planned sales = $85K × 1.12 = $95,200 for November.
Planned End-of-Month (EOM) Inventory
The target inventory level at the end of the planning period. Typically expressed as a stock-to-sales ratio or in weeks of supply. Setting this correctly prevents both month-end stockouts and excessive carryover.
Formula
Planned EOM Inventory = Planned Next Month Sales × Stock-to-Sales Ratio TargetExample: Planned December sales: $120K. Target stock-to-sales ratio: 2.5. Planned EOM inventory at end of November = $120K × 2.5 = $300K (to enter December with proper coverage).
On-Order Inventory
The value of purchase orders already placed but not yet received. Reduces the OTB budget because this inventory commitment is already made - it will arrive and count against planned EOM inventory targets.
Formula
On-Order Value = Σ (Units × Landed Cost per Unit) for all open POs expected to arrive in periodExample: Three open POs totaling $42,000 in landed cost are expected to arrive this month. On-order = $42,000. This reduces the OTB budget by $42,000 before any new purchasing.
Markdown Budget
The planned reduction in retail value due to promotional discounts, clearance pricing, and returns. Reducing planned markdowns increases OTB - because lower markdowns mean more of your planned sales are captured at full price with less inventory.
Formula
Markdown % = Total Markdowns / Net Sales × 100Example: If you plan $12,000 in markdowns on $100,000 of planned sales, your markdown rate is 12%. Best-in-class DTC operations often target 8–10% markdown rates; fashion can run 15–20% in clearance periods.
Why native Shopify isn't enough
While Shopify is a strong commerce engine, its native inventory tooling often reaches a limit once brands need better forecasting, replenishment logic, supplier workflows, and purchasing discipline.
- Shopify does not ship a native open-to-buy planner; its education content defines and explains OTB but explicitly points merchants to third-party apps to actually implement it.
- There is no Shopify-native mechanism to set a monthly buying budget, track POs against that budget, and alert when remaining OTB drops below a threshold.
- Shopify's PO and transfer features track what has been ordered but provide no forward-looking budget or commitment tracking that an OTB process requires.
- Tools like Inventory Planner, Toolio, and Lila compute OTB for Shopify merchants, but native Shopify itself plays only the role of data source (sales and inventory feeds) in these workflows.
Key stats and benchmarks
Shopify's own content on OTB documents the formula and benefits but explicitly does not offer a native implementation - directing merchants to third-party apps for actual OTB functionality.
Merchants who implement OTB planning report fewer end-of-season overstock positions and an average 10–20% reduction in average inventory investment within two planning cycles.
US retailers lose $362 billion per year to excess inventory - a significant portion of which is preventable with proper upfront buying budget discipline (OTB).
Brands operating without OTB commonly discover overstock problems only when cash becomes tight - typically 60–90 days after the over-buying decision, when it's too late to cancel orders.
OTB tools for Shopify such as Inventory Planner, Lila, and Toolio command significant monthly fees (often $200–$500+/month) - reflecting real demand for planning capabilities that Shopify doesn't provide natively.
Practical angles to explore
- OTB for Shopify beginners: a step-by-step walkthrough of your first open-to-buy plan using only Shopify export data and a spreadsheet
- The OTB formula explained with Shopify data: where to find each input in your Shopify reports
- Monthly OTB review process: how to run a 30-minute buying budget review at the start of each month
- OTB and cash flow: how open-to-buy connects to your working capital position and cash flow forecast
- Seasonal OTB planning: how to build a full-year OTB calendar for a fashion or seasonal goods brand
How Synplex helps
Synplex brings OTB logic to Shopify-native buying: it uses your demand forecasts and planned inventory targets to compute a forward-looking buying budget, tracks POs against that budget in real time, and flags when Smart Replenishment suggestions would push total commitments over the OTB limit - turning OTB from a spreadsheet exercise into a live guardrail on purchasing decisions.
- OTB calculation using demand forecast, inventory targets, and live Shopify data
- Open PO commitment tracking that reduces remaining OTB in real time as orders are placed
- Monthly buying budget dashboard with remaining OTB by category
- Alerts when Smart Replenishment suggestions would exceed OTB budget
- Seasonal OTB planning view across a 12-month forward horizon
Suggested guide outline
- 1Intro: Why over-buying is the single biggest preventable cash flow mistake in ecommerce
- 2Section 1: Open-to-buy explained - the concept, the formula, and who needs it
- 3Section 2: The OTB formula with Shopify - where to find each input
- 4Section 3: Step-by-step: building your first monthly OTB plan from Shopify data
- 5Section 4: Seasonal OTB planning - how to extend the framework across a full year
- 6Section 5: Running the monthly OTB review - a 30-minute process for Shopify teams
- 7Section 6: OTB vs. reorder points - how they work together in a complete planning system
- 8Section 7: How Synplex turns OTB from a spreadsheet into a live buying guardrail
Frequently asked questions
Common questions about open-to-buy planning for shopify brands: the buying budget framework.