Effective Date: August 10, 2026

Proper packaging protects your item, reduces delivery problems, and helps prevent shipping adjustments. Sellers are responsible for accurately weighing, measuring, packaging, labeling, and shipping their orders in compliance with Mercado Sales policies and the carrier’s requirements.

These guidelines apply to domestic shipments within the United States.

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1. Determine the Billable Shipping Weight

Weigh and measure the item after it has been completely packaged. Include:

  • The shipping box or mailer;
  • Protective wrapping;
  • Cushioning materials;
  • Accessories and documentation;
  • Tape; and
  • Any other material placed inside or attached to the package.

Depending on the carrier and shipping service, the billable weight may be the greater of:

  • The package’s actual weight; or
  • Its dimensional weight.

Dimensional Weight

Dimensional weight reflects the amount of space a package occupies in the carrier’s network. It is generally calculated using:

Length × Width × Height ÷ carrier’s dimensional divisor

Measure the package’s exterior at its longest, widest, and tallest points. Follow the carrier’s rules for rounding measurements and weight.

The dimensional divisor can vary by carrier, service, rate type, and applicable carrier agreement. Do not assume that 139 applies to every Mercado Sales label. Use the divisor and calculation displayed for the selected shipping service.

Example Using a Divisor of 139

  • Actual packaged weight: 5 lb
  • Length: 20 inches
  • Width: 12 inches
  • Height: 8 inches

Dimensional weight: (20 × 12 × 8) ÷ 139 = 13.81 lb

If the carrier requires rounding to the next whole pound, the billable dimensional weight would be 14 lb, not 13 lb.

Because the dimensional weight is greater than the actual weight, a label covering at least 14 lb would be required in this example.

Important Weight Rules

  • Every ounce matters, especially for lightweight USPS packages.
  • Weigh the complete, sealed package—not only the item.
  • Most carrier services round chargeable fractional pounds to the next whole pound.
  • For example, a package weighing 3 lb 4 oz may be charged at the 4 lb rate.
  • Enter accurate exterior dimensions, including bulges and irregular sections.
  • The seller is responsible for postage adjustments, overage charges, penalties, or other expenses resulting from inaccurate weight, dimensions, packaging, or service selection.

Carrier rules can change. Sellers should confirm the current requirements before shipping. USPS confirms that postage may be rounded to the next available ounce or pound rate depending on the service. USPS postage verification guidance.

2. Select the Correct Packaging

Use packaging that is appropriate for the item and accepted by the selected carrier and service.

Soft Goods and Flexible Items

For clothing and other durable, non-fragile items, you may use:

  • A shipping envelope;
  • A poly mailer; or
  • Another carrier-approved soft package.

Protect the item from moisture and avoid using packaging that could tear during sorting.

Fragile or Rigid Items

Use a sturdy corrugated cardboard box for:

  • Fragile items;
  • Rigid or non-bendable items;
  • Electronics;
  • Collectibles;
  • Shoes; and
  • Products that could be crushed or damaged in a mailer.

Use the smallest suitable box that still provides enough room for appropriate cushioning.

Retail Packaging

Do not assume that a manufacturer’s or retail box is strong enough for shipping. Place retail packaging inside a separate shipping box unless the original packaging was specifically designed and approved for shipment.

Do not attach a shipping label directly to collectible, branded, or valuable retail packaging.

Reused Boxes

Shipping boxes may be reused if they remain clean, dry, sturdy, and undamaged.

Completely remove or permanently cover:

  • Previous shipping labels;
  • Barcodes;
  • Tracking numbers;
  • Addresses; and
  • Old handling or hazardous-material markings that do not apply to the current shipment.

Do not turn a box inside out if doing so weakens its structure.

If the current shipment contains regulated materials, retain or apply every marking required by the carrier and applicable law.

Carrier-Branded Packaging

Use carrier-provided packaging only with the corresponding carrier and eligible service.

For example, USPS Priority Mail packaging must not be used with USPS Ground Advantage or another non-Priority Mail service.

If the selected Mercado Sales label does not accommodate the package, choose another available service or use the approved “Ship on Your Own” option, if offered.

3. Pack the Item Securely

Sellers are responsible for packaging items so they can withstand ordinary carrier handling.

Cushioning

  • Wrap fragile items individually.
  • Separate multiple items with at least one inch of cushioning when appropriate.
  • Protect sharp edges and protruding components.
  • Add cushioning around every vulnerable side.
  • Fill empty space so the contents do not shift during transit.
  • Use additional protection for glass, ceramics, electronics, and other delicate products.

Before sealing the package, gently shake it. If the contents move, add more cushioning.

Liquids

Place permitted liquids in a sealed container and use secondary leak-resistant packaging. Add absorbent and cushioning material when appropriate.

Liquids, perfumes, cosmetics, aerosols, and similar products may be restricted by Mercado Sales or the carrier. Confirm that the item is permitted and that the selected service can legally transport it.

Sealing the Package

Use durable shipping tape on:

  • The center seam;
  • Side seams; and
  • Every opening through which the package could separate.

Do not use masking tape, gift-wrapping tape, string, or another material not designed for parcel shipping.

Documentation

Before shipment, photograph:

  • The item’s condition;
  • Serial numbers or identifying marks when applicable;
  • The item inside its protective packaging;
  • The sealed package; and
  • The shipping label attached to the package.

Keep these photographs and the carrier receipt until the transaction is completed.

A “Fragile” marking does not replace proper packaging and does not guarantee special carrier handling.

4. USPS Media Mail

USPS Media Mail may be used only for qualifying materials. Eligible content can include certain:

  • Books containing at least eight pages;
  • Printed music;
  • Playscripts and manuscripts;
  • Sound recordings; and
  • Video recordings.

Video games, computer drives, digital drives, merchandise, and many advertising materials do not qualify.

Media Mail packages are subject to USPS inspection. Using Media Mail for ineligible contents may result in delayed delivery, postage adjustments, penalties, or postage due.

The seller is responsible for confirming eligibility and paying charges resulting from incorrect use. Review the official USPS Media Mail requirements before selecting this service.

5. USPS First-Class Mail Envelopes

If Mercado Sales offers a USPS First-Class Mail envelope option for eligible trading cards, sellers must follow the dimensions, thickness, flexibility, weight, and content limitations displayed when purchasing the label.

A standard machinable envelope generally must not exceed:

  • 11½ inches in length;
  • 6⅛ inches in height; and
  • ¼ inch in thickness.

An envelope that is rigid, uneven, excessively thick, or otherwise non-machinable may incur additional postage or be rejected.

Do not use this service for objects that could damage postal equipment or that do not satisfy the selected label’s requirements.

6. Batteries and Hazardous or Restricted Materials

Mercado Sales prohibits items identified as prohibited under its Prohibited Items Policy. Some permitted products may nevertheless be regulated by USPS, UPS, FedEx, the Department of Transportation, or another authority.

Examples can include:

  • Lithium batteries;
  • Perfume and alcohol-based products;
  • Aerosols;
  • Flammable liquids;
  • Certain cleaning products;
  • Pressurized containers; and
  • Items containing magnets or other regulated components.

Lithium Batteries

Do not automatically remove a lithium battery from a device. Whether a battery may be shipped installed in equipment, packed with equipment, or separately depends on:

  • Battery type;
  • Battery capacity;
  • Battery condition;
  • Quantity;
  • Packaging;
  • Carrier; and
  • Transportation method.

Damaged, defective, swollen, or recalled batteries may be prohibited.

USPS permits certain domestic shipments containing lithium batteries only when all applicable packaging, quantity, service, and marking requirements are satisfied. Consult the current USPS Publication 52 and the selected carrier’s rules before shipping.

Required Declarations and Labels

Sellers must accurately declare regulated contents and use the required service, packaging, and markings.

Never:

  • Conceal hazardous or regulated contents;
  • Use a service that does not accept the contents;
  • Remove a required marking;
  • Reuse an unrelated hazardous-material label; or
  • Ship a prohibited or leaking product.

Additional carrier charges or noncompliance fees may apply to improperly prepared hazardous-material shipments.

7. Oversized and Heavy Packages

Mercado Sales prepaid labels, if available, may have maximum weight and size limits that are lower than the carrier’s general limits.

The seller must review the limits displayed for the selected label. If the packaged item exceeds those limits, the seller must choose another eligible shipping method or use the approved “Ship on Your Own” option.

Do not purchase a lower-weight label or enter smaller dimensions to avoid shipping charges.

Packages weighing more than 50 lb, or exceeding any dimension shown for the available Mercado Sales labels, may require the seller to ship independently using a supported tracked service.

Oversized or unusually shaped packages may be subject to:

  • Additional-handling charges;
  • Large-package surcharges;
  • Nonstandard-dimension fees;
  • Dimensional-weight pricing; or
  • Carrier rejection.

8. Ship the Order

Unless the listing or order states otherwise, the seller must deliver the package to the correct carrier within three business days after the sale, excluding carrier-observed holidays.

After giving the package to the carrier:

  • 1. Obtain a carrier receipt or acceptance confirmation.
  • 2. Confirm that the tracking number is correct.
  • 3. Update the order status to “Shipped.”
  • 4. Keep the receipt until the transaction is completed.

Scanning a label or marking an order as shipped before transferring the package to the carrier is prohibited.

Use the Correct Carrier

A package must be given to the carrier identified on its label.

For example:

  • Do not leave a UPS package at a USPS location unless the selected UPS service and facility expressly permit it.
  • Do not leave a FedEx package at USPS.
  • UPS Ground Saver and similar consolidated services must be tendered according to the instructions printed on the label.
  • USPS cannot accept packages bearing only UPS or FedEx labels.

Using the wrong carrier can cause delays, loss of tracking, return of the package, additional charges, or loss of shipping protection.

9. Seller Responsibility

Failure to follow these requirements may result in:

  • Postage adjustments;
  • Deduction of carrier charges from seller proceeds;
  • Delayed or returned shipments;
  • Denial of shipping or seller protection;
  • Cancellation of the transaction;
  • Account restrictions; or
  • Other action permitted under Mercado Sales policies.

Carrier requirements control when they are more restrictive than these general guidelines.

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