Demand Planner & Buyer

Thrivin; Southampton; On-site; GBP 45,000 - 65,000; Full time

Job summary

Thrivin, a fast-growing global activewear brand, seeks an experienced Demand Planner & Buyer to own demand forecasting, purchasing and inventory management. You will drive open-to-buy, replenishment cycles and stock health, partnering with product, operations and commercial teams to optimise availability and performance.

You will personally own planning decisions, manage PO lifecycles and work closely with suppliers to ensure timely deliveries and strong sell-through in a high-volume ecommerce

Qualifications

• Own planning and buying decisions within apparel.
• 5+ years' experience in apparel planning/buying.
• Experience owning an open-to-buy and making buying decisions.
• Hands-on experience creating and placing purchase orders.
• Strong supplier-facing experience with MOQs, lead times and invoices.
• Advanced Excel proficiency for large datasets.

Responsibilities

• Own open-to-buy by category, including sales forecasts and monthly plans.
• Run the bi-weekly replenishment cycle end-to-end and submit POs.
• Determine newness buy quantities by style, colour and size to align with launches.
• Manage full PO lifecycle: creation, amendments, invoicing and tracking.
• Maintain healthy inventory levels and in-stock rates.
• Monitor stock risks and optimize markdowns/inventory health.
• Lead planning insights during weekly/monthly trade reviews.
• Collaborate with suppliers on proforma invoices, MOQs, and delivery timelines.

Skills

Demand planning

Inventory management

Open-to-buy (OTB)

Purchase orders

Excel

Data analysis

Supplier management

Ecommerce / Retail

Claude Code

Claude Cowork

Tools

Claude Code

Claude Cowork

Job description

Thrivin is a fast-growing global activewear brand operating in a high-volume, fast-paced ecommerce environment. As we continue to scale internationally, we're looking for an experienced Demand Planner & Buyer to take ownership of our demand planning, purchasing and inventory management across the business.

This is a highly hands-on role for someone who is commercially sharp, analytical and comfortable taking full ownership. You'll play a critical role in ensuring we have the right product, in the right quantities, at the right time, balancing availability, inventory health and commercial performance.

The Role

As Demand Planner & Buyer, you will own the planning and buying process from sales forecasting and open-to-buy management through to purchase order placement, replenishment and inventory optimisation.

You'll work closely with the wider product, operations and commercial teams, providing clear recommendations and insights to support trading decisions and future growth.

Key Responsibilities

• Own the open-to-buy (OTB) by category, including sales forecasts, receipt plans and monthly plan vs. actual performance.
• Run the bi-weekly replenishment cycle end-to-end, from analysing demand and stock requirements through to PO submission.
• Determine newness buy quantities at style, colour and size level, ensuring buys are aligned with launch dates, expected demand and commercial targets.
• Own the full purchase order lifecycle, including PO creation, submission, amendments, invoice reconciliation, ETA tracking and supplier follow-ups.
• Own inventory management across categories, maintaining healthy stock levels and strong size availability and in-stock rates.
• Monitor inventory performance and proactively identify potential stock risks, shortages and excess inventory.
• Own markdown and overstock actions, recommending commercially appropriate strategies to optimise sell-through and inventory health.
• Analyse key planning and trading metrics including weeks of cover, sell-through, size curves, gross margin, discount rate and in-stock performance.
• Deliver the planning read and key insights during weekly and monthly trade reviews.
• Work directly with suppliers on proforma invoices, MOQs, lead times, purchase orders and delivery timelines.
• Identify discrepancies, risks and unusual data points early and investigate them before they impact buying or inventory decisions.
• Continuously improve planning processes, reporting and ways of working as Thrivin scales.

About You

We're looking for someone who has personally owned planning and buying decisions within an apparel environment. You won't simply have supported an OTB or PO process, you'll have been directly accountable for it.

Experience & Technical Skills

• 5+ years' experience within apparel planning, merchandising, buying or a closely related field, ideally within a high-volume ecommerce or retail environment.
• Previous management or leadership experience is preferred.
• Demonstrable experience personally owning an open-to-buy and making commercial buying decisions.
• Hands-on experience creating and placing purchase orders.
• Strong understanding of planning fundamentals, including:
• Weeks of cover
• Sell-through
• Size curves
• In-stock rate / availability
• Gross margin
• Discount rate
• Inventory turn and stock health
• Strong supplier-facing experience, including working with proforma invoices, MOQs, lead times and order chasing.
• Advanced proficiency in Excel and confidence working with large datasets.
• High proficiency using Claude Code and/or Claude Cowork to improve efficiency, analysis and workflows.
• Experience within a high-growth DTC, ecommerce, fashion or activewear business would be highly advantageous.

Why Join Thrivin?

This is an opportunity to take meaningful ownership of a critical commercial function within a rapidly scaling global ecommerce brand. You'll have significant autonomy, direct visibility into business performance and the opportunity to help shape how Thrivin approaches demand planning, buying and inventory management as we continue to grow.