Same stock on your website and marketplaces: how not to oversell on Black Friday

.comparison-cards { display: flex; flex-direction: column; gap: 1.5rem; } .comparison-card { background: #fff; border-radius: 16px; padding: 20px; border: 2px solid #efefef; } .comparison-header { display: flex; justify-content: space-between; font-size: 16px; margin-bottom: 12px; } .comparison-row { display: flex; justify-content: space-between; padding: 8px 0; border-top: 1px solid #efefef; font-size: 14px; color: #1f2937; } .comparison-label { font-size: 14px; width: 30%; } .comparison-value { width: 65%; text-align: right; } @media (max-width: 600px) { .comparison-row { flex-direction: column; align-items: flex-start; } .comparison-value { text-align: left; margin-top: 4px; } } You sell the same products on your website and on a marketplace such as eMAG, maybe on another one too, from the same shelf. All year it works, because a few orders come in each day and you have time to correct the stock. In Black Friday week (Friday, 27 November 2026) and up to Cyber Monday (30 November), the pace changes: the same last unit can be bought in two places within the same quarter of an hour. The result is a cancelled order, an unhappy customer and, on the marketplace, a bad mark on your seller record. Below is how I organise shared stock so you don't sell what you don't have. 1. Why the same unit gets sold twice Overselling almost never comes from a single mistake. Usually several add up: Sync delay: stock updates once an hour or once a day, and in between both channels see the old number. Manual updates: someone uploads a stock file in the morning, and by the afternoon it is already out of date. Different codes: the "M, blue" variant has one SKU on the website and another on the marketplace, so an order on one channel does not reduce stock on the other. Bundles and sets: the set has its own stock, separate from the products inside it. Returns and a physical shop: returned items or items sold over the counter don't reach the system in time. 2. One source for stock The basic…