Which ink/toner does the HP LaserJet MFP M140we use?

The HP LaserJet MFP M140we (laser, 2022) uses W1420A.

Compatible cartridges

CartridgeColorYieldPagesOEM priceCost/page
W1420A black standard950 $55.00 5.8¢ OEM · AmazonCompatible

XL/high-yield cartridges usually cost more upfront but lower the cost-per-page — better if you print often.