“Invalid values in label stock type for label” means the label stock type your shipping software sent to FedEx doesn’t match the label it’s trying to print. Usually a thermal stock value (such as STOCK_4X6) went out with a PDF or PNG image, or a paper stock value (such as PAPER_4X6) went out with a ZPLII or EPL2 thermal image. The fix is to make the stock type, the image type and your printer agree, then generate the label again.
The error is a setup problem, not a problem with the shipment. Nothing is wrong with the address, the weight or the service. FedEx’s label server rejected the format request before it built a label, so no label was created and nothing needs to be voided.
What Does “Invalid Values in Label Stock Type for Label” Mean?
Every FedEx label request includes a label specification with three settings: the label format type, the image type (the file or printer language returned), and the label stock type (the size and layout of the stock the label prints on). FedEx’s Ship API documentation says the label stock type is required for all label types. It describes the setting as the stock’s size and whether it has a Doc-Tab on the leading or trailing end, or no Doc-Tab.
The error appears when the stock value is one FedEx won’t accept for that request. In practice that comes down to three causes:
- Stock and image type don’t match. PAPER_ values are for PDF and PNG images printed on laser printers. Thermal stock values are for the ZPLII (Zebra) and EPL2 (Eltron) printer languages.
- The value isn’t valid for that document. Some documents, such as certain return, freight or international paperwork, support only some stock sizes, and a setting that works for a standard shipping label can fail on them.
- The value is blank or misspelled. A custom integration that sends an empty field, a lowercase value or a retired value gets the same rejection.
“Stock” here means the label’s size and layout, not its material. The old explanation still circulating online, that the error comes from choosing vinyl instead of paper, doesn’t match how FedEx defines the field. No FedEx stock value describes a material.
Which Label Stock Types Work With Which Image Types?
The FedEx Ship API splits its stock values into laser (paper) and thermal (stock) families. Pick the family that matches your printer, then the size that matches the labels loaded in it.
| Printer | Image type | Stock family | Common values |
|---|---|---|---|
| Laser, 4 x 6 or similar label sheets | PDF or PNG | PAPER_ (laser label) | PAPER_4X6, PAPER_4X675, PAPER_4X8, PAPER_4X9 |
| Laser, plain letter paper | PDF or PNG | PAPER_ (plain paper) | PAPER_85X11_TOP_HALF_LABEL, PAPER_85X11_BOTTOM_HALF_LABEL, PAPER_LETTER, PAPER_7X475 |
| Zebra thermal | ZPLII | STOCK_ (thermal) | 4 x 6, 4 x 6.75, 4 x 8 and 4 x 9 stock, with or without a Doc-Tab |
| Eltron thermal | EPL2 | STOCK_ (thermal) | Same thermal sizes as ZPLII |
Two FedEx printing rules are worth knowing while you’re in these settings. FedEx says its laser labels won’t be accepted if printed on an inkjet printer, and that 4 x 6 PNG labels must go on peel-and-stick stock, not plain paper. If you print to a color laser, set the color to black.
How Do You Fix the Label Stock Type Error?
- Identify your printer. A desktop laser or inkjet printing on sheets needs a PDF or PNG image. A direct thermal printer such as a Zebra needs ZPLII (or EPL2 on older Eltron models).
- Open the label settings in your shipping tool. Look for “label format”, “printer type”, “label stock” or “label size”. In a custom API integration, it’s the label specification object in the ship request.
- Match the stock to the image type. Use a PAPER_ value with PDF or PNG and a thermal STOCK_ value with ZPLII or EPL2. Don’t mix families.
- Match the size to the labels actually loaded. If you load 4 x 6 thermal labels with no tab, choose the 4 x 6 thermal stock, not a Doc-Tab variant.
- Check document-specific settings. If the error only appears for one document, such as a return label or a freight address label, that document has its own stock setting. Set it separately.
- Regenerate the label. Because the rejected request never produced a label, you can simply resubmit. Our walkthrough of how to create a FedEx label covers the rest of the flow.
If you changed your stock setting after a label was already printed, the old label is still valid. Only reprint it if the format is wrong for your printer; see how to edit a FedEx shipping label after printing for what you can and can’t change.
Why Does the Error Start After a Printer or Software Change?
The error usually shows up right after something in the print chain changes. Common triggers are switching from a laser printer to a thermal printer without changing the image type, connecting a new shipping app that defaults to letter-size PDFs, or updating an integration to FedEx’s newer REST APIs, where field names and allowed values differ from the older web services.
A quick test isolates the cause. Print one label as a plain PDF on PAPER_85X11_TOP_HALF_LABEL. If that works, the account and shipment are fine and the problem is only the thermal settings. If even that fails, the integration is sending a bad or empty value and its developer needs to check the request.
Does the Label Stock You Buy Matter?
The physical stock has to match the setting, or the label will print but scan badly. A 4 x 6 thermal label printed on 4 x 8 stock, or a half-sheet PDF scaled down to fit a 4 x 6 label, can distort the barcode. FedEx says printer scaling should be set to none for PDF labels.
Direct thermal printers need direct thermal labels. Laser printers need laser-safe adhesive sheets or plain paper placed in a pouch. Our guide to labels and printers for shipping compares common printer and stock setups, and the FedEx labels and supplies guide covers what FedEx itself provides.
Do UPS and USPS Labels Have the Same Problem?
The idea is the same at every carrier: the label format has to match the printer. UPS and USPS labels are standard 4 x 6 shipping labels that print as a PDF or image on a laser printer or as a thermal label. A mismatch there tends to produce a badly sized label rather than this exact FedEx error message. The UPS shipping label guide explains what a UPS label needs.
If you ship with UPS or USPS, ParcelPath creates discounted labels for both carriers and can skip the printer entirely. UPS Mobile Barcode labels print at UPS Store locations, and USPS Label Broker labels print at the Post Office. For FedEx shipments, our FedEx shipping hub covers labels, tracking and services.
Frequently Asked Questions
What does “invalid values in label stock type for label” mean?
It means FedEx rejected the label stock type in the label request because it isn’t valid for that label. The usual cause is a mismatch between stock and image type, such as a thermal stock value sent with a PDF image or a PAPER_ value sent with a ZPLII thermal image. Matching the stock family to the image type and printer clears the error.
Is this error caused by using vinyl labels instead of paper?
No. In FedEx’s label specification, the stock type describes the label’s size and layout, such as 4 x 6 or a half sheet of letter paper, and whether it has a Doc-Tab. It doesn’t describe the material. The error comes from a size or format value that doesn’t fit the image type or document, not from the label material.
Which label stock type should I use with a Zebra thermal printer?
Use the ZPLII image type with a thermal stock value that matches the labels loaded, most often 4 x 6 thermal stock without a Doc-Tab. Use the Doc-Tab versions only if your labels have the extra tear-off tab. PAPER_ values are for PDF or PNG labels on laser printers and will trigger the error with ZPLII.
Do I need to void anything after this error?
No. The rejection happens before FedEx generates a label, so no tracking number is created and there’s nothing to cancel. Correct the stock type setting and submit the label request again. If labels were already printed in the wrong size, void those through your shipping tool before reprinting so they aren’t billed.
Sources
- FedEx Developer Portal: Ship API documentation, Label Specification (LabelFormatType, ImageType, LabelStockType), developer.fedex.com
- FedEx Developer Portal: Ship API laser and thermal label requirements (inkjet, peel-and-stick and printer-scaling rules), developer.fedex.com
Part of our Labels and Printers guide. Related: Printing Shipping Labels at Home, Bulk Mailing Labels, Email Prepaid Shipping Label, and our Shipping Resources library.
