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1. Go to Inventory → Supplies → Import/Export then select Export Supplies.
Note: It's best to save a back up backup copy of your supply list prior to making changes so you'll have something to go back to if need to revert some changes.
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In this example, our fist item has a sell price of $10.2 which is 40% 50% markup. To update it to 50% 60% markup, we can calculate by $10.00 X 60% + Cost Ex tax = $16.3200. If you're using formulas to calcuate the new markup, make sure to paste the data as values prior to importing. 
Prior to the change
After updating column J Sell Price based on 60% markup
6. Save the updated file and go back to Inventory → Supplies → but this time, select Import and markup for the selected supply category should update accordingly.
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