When a shipping label won't scan, the cause is almost always physical: faded ink, a barcode stretched or shrunk by print scaling, glare from tape laid across the bars, or a crease running through the code. Nearly every case has a two-minute fix — reprint at 100% scale, re-tape with the barcode clear, or ask the clerk to key in the number manually — and if the label itself is defective, you void it and reprint at no real cost, since an unused label can be voided and the money returns to you.

Why do printed labels fail to scan?

A barcode is just a pattern of dark bars and light spaces at precise widths. The scanner shines light at it and reads the reflections. Anything that blurs, distorts, dims, or shines where it shouldn't makes the pattern unreadable. In practice the failures cluster into a short list:

Symptom	Root cause	The fix
Faded or banded bars	Inkjet cartridge running dry, or draft/economy print mode	Replace the cartridge or switch to normal quality; reprint
Barcode looks stretched or tiny	"Fit to page" or custom scaling changed bar widths	Reprint at 100% / actual size
Bars look fine but the scanner glares off	Glossy tape laid directly over the barcode	Re-tape with the barcode uncovered, or overlay a clean reprint
Smeared or wet-looking print	Inkjet ink not dry, or damp label stock	Let it dry before taping; reprint if smeared
Crease or wrinkle through the code	Label applied over a box seam or curved edge	Move the label to a flat panel; reprint if damaged
Scans at home, fails at the counter	Low-contrast print marginal for industrial scanners	Reprint darker — phone cameras forgive more than sort machines

Notice what is not on the list: the label data itself. If the address and postage are valid, the information encoded in the barcode is fine — the failure is in how the pattern made it onto paper. That is good news, because paper problems are cheap to fix.

Which print settings quietly ruin barcodes?

Three settings cause the large majority of self-inflicted scan failures:

Scaling. PDF viewers love "fit to page," and fit-to-page resizes the barcode. Bar widths are the data — change them a few percent and marginal scanners start misreading. Always print shipping labels at 100% / actual size. If you print on 8.5x11 paper, the label should occupy its natural area of the sheet, not be inflated to fill it.

Draft mode. Economy and draft modes lay down less ink to save cartridges. On text you barely notice; on a barcode it drops contrast below what conveyor scanners want. Print labels at normal quality even if everything else you print is draft.

Wrong paper size on thermal printers. A 4x6 thermal printer set to letter-size output will compress or clip the label. Set the driver's paper size to 4x6 once and it stays fixed. (This is one of several reasons thermal printers produce the most reliable barcodes — once configured, there is nothing to get wrong per print.)

And one physical habit that belongs with the settings: tape placement. Tape all four edges of a paper label, but never lay tape across the barcode itself. Glossy tape creates specular glare — the scanner sees its own light bounced back and reads nothing. If you must fully weatherproof a label, use a clear packing-list pouch designed to be scanned through, not a strip of tape.

How do you rescue a label that is already on the box?

The label is taped down, the box is sealed, and the barcode won't read. In order of effort:

Ask for a manual entry. Every barcode has its number printed beneath it in human-readable digits. A retail clerk can key that number in and accept the package. This is the fastest rescue at a staffed counter — it just doesn't help at self-service dropboxes, where nobody is there to type.
Flatten and clean. If the label is wrinkled, press it flat; if it is dusty or scuffed, wipe it gently. Scanners are more forgiving of a flat, clean, imperfect print than a crisp one under a wrinkle.
Reprint and overlay. Print the same label again — same purchase, same barcode, no new charge — and tape the fresh copy directly over the failed one on a flat panel of the box. This is the reliable fix when the original print itself was bad.
Relocate. If the label was applied over a seam, an edge, or a curved surface, the overlay is also your chance to move it to the largest flat face of the package.

A useful habit that prevents the counter surprise entirely: after printing, scan the barcode yourself with your phone camera. If your phone struggles in good light, an industrial scanner reading packages on a moving belt will struggle more. Ten seconds at home beats a second trip to the drop-off point.

When should you void and reprint instead?

Reprinting the same label is free and fixes print-quality problems. Voiding is for when the label itself is wrong — or gone:

Wrong data. The address, weight, or service is incorrect. Do not ship a mislabeled package and hope; void the label, fix the details, and buy a fresh one.
Damaged beyond overlay. The file is fine but the physical situation is a mess — soaked box, torn label with no clean panel left. Repack, void if you are switching anything, or just reprint onto the new box.
The label was never used and plans changed. The order cancelled, or you re-quoted and found a better rate. Void it rather than letting it expire.

The mechanics matter here: a voided, unused GoatLabels label is refunded to your wallet balance, where the money is immediately spendable on the replacement label — you are not waiting on a card reversal to clear before you can ship. Carriers set an outside window for unused-label refunds, so void promptly rather than letting dead labels pile up. And never reuse a voided label's barcode: once voided, that postage is cancelled, and the package will be stopped or returned.

How do you stop it from happening again?

Scan failures are a solved problem once your setup removes the failure modes:

Lock in the print settings. 100% scale, normal quality, correct paper size — set once, never touched again.
Keep tape off barcodes as a hard rule, or eliminate tape entirely with self-adhesive thermal labels.
Watch the ink. If you stay on inkjet, treat a slightly faded label as a stop sign, not a shrug. The next one will be worse.
Upgrade when volume justifies it. A 4x6 direct-thermal printer removes ink, tape, and scaling from the equation in one purchase — the cost math is in our thermal vs inkjet breakdown.
Phone-check anything questionable before it leaves the house.

Every label you buy on GoatLabels — USPS, UPS, FedEx, or DHL, rate-shopped on one screen — renders as a standard PDF built for clean printing at 4x6 or on letter paper. Get the physical layer right and the barcode takes care of itself.

FAQ

Can I reprint the same label without paying again? Yes. Reprinting an already-purchased label is just printing the same file again — same barcode, no new charge. Only buying a new label costs money, and voiding the unused one recovers that.

The clerk keyed my package in manually — will it track normally? Yes. Manual entry gets the package accepted into the system; downstream automated scanners will usually read the physical barcode fine once the package is moving, and tracking events post normally.

Will a package with an unscannable barcode still be delivered? Often, but slowly and riskily — it falls out of automated sorting into manual handling. Treat an unscannable label as a defect to fix before drop-off, not something to gamble a buyer's order on.

Does it matter if the barcode scans but looks ugly? If it reliably scans — including on your phone-camera check — cosmetic ugliness is irrelevant. Contrast and correct bar widths are the only beauty standards a sort machine has.

My label got wet and the print ran — now what? If the barcode is compromised, reprint the label and overlay it on a dry, flat panel, or repack into a dry box and apply the reprint there. Inkjet ink runs when wet; thermal and laser prints resist it better.