How do I get my in-stock inventory automatically deducted once my sales is created?

If you want to have your inventory deduct automatically right after you have created the Sales Order then you need to set the automatic function.
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Go to Company Settings > Basic Settings > Automatic Function > tick "Automatically convert to Shipment after creating a Sales Order."
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Once a Sales Order is created, EMERGE App will automatically convert the Sales Order to a Delivered shipment and your inventory will deduct immediately.