Guide to USPS First-Class Mail Letter shipping

If you're a seller in the US, selling cards or stickers from live shows, USPS First-Class Mail Letter (FCML) can be a simple, affordable way to ship small orders in a standard envelope. No fancy packaging needed.

Also known as plain white envelope (PWE) shipping, this option helps keep costs low for you and your buyers.

On this page: 

• When to use FCML
• Why sellers use FCML
• How much FCML costs
• Turn on First-Class Mail Letter shipping
• FCML envelope requirements
• FCML shipping time and limited tracking
• If your shipment doesn't qualify for FCML
• FAQs

When to use FCML

You can use FCML if: 

• Item criteria:
  • You're selling in Trading Card Games, Sports Cards, or Stickers categories
  • You're selling these items during a live show
  • Your item isn’t listed using a custom shipping profile / max bundle size
• Shipping requirements:
  • The shipment includes no more than 5 items/cards
  • The total shipment weighs 3 oz or less
  • The total shipment value is $20 or under
  • The buyer is in the US (domestic shipping only) 

Why sellers use FCML

• Cheaper shipping costs: Label prices start at $0.74 (+ fees*).
• Easier to pack: Just use a standard paper business envelope and print the label from Whatnot.
• Faster to drop off: Drop the envelope in any USPS mailbox and skip a trip to the post office. 

How much FCML costs

As of July 13, 2025, FCML labels prices are:

* The total shipping cost for FCML includes the label price listed above, plus a small fee to help cover the operational cost of features like Smart Bundling and Flat-Rate shipping. Whatnot continues to invest in great product experiences and work with our carriers to get preferential rates for our customers. 

Turn on First-Class Mail Letter shipping

Turn FCML on for future shows

If you’re selling items that qualify for First-Class Mail Letter, you can turn it on in your Seller Hub shipping settings. Once it’s on, FCML will automatically apply to eligible orders for future shows.

Note: You can only turn FCML on from your Seller Hub in the Whatnot app. 

Update FCML for a scheduled show

You can also enable FCML for an upcoming show you already scheduled. If it’s a recurring show, these changes will apply to all future instances of that show. 

FCML envelope requirements

When packing an FCML shipment, use a standard paper envelope or flat paper mailer that meets all of these USPS requirements:

• Length: 5–11½ inches
• Width: 3½–6⅛ inches
• Thickness: ¼ inch max, with even thickness and no lumps
• Proportional aspect ratio (length ÷ height): 1.3 to 2.5
  • Example: A 6.5 x 4.25" envelope is OK because the aspect ratio = 1.53

Not accepted: 

• Envelopes with clasps, strings, or buttons
• Plastic sleeves, bubble mailers, cardboard, or other rigid packaging
• Anything that feels stiff, uneven, or can't bend easily 

Sticking to these guidelines helps avoid USPS surcharges, returns, or delays. 

FCML shipping time and limited tracking 

First-Class Mail Letter is a slower shipping option. Orders usually arrive in 2 to 10 business days, depending on USPS and the buyer’s location.

Tracking is limited and only visible on Whatnot. It won’t appear on the USPS website.

You may see up to 3 tracking updates in your Order Status page:

• In transit (accepted by USPS)
• Processing (scanned at a USPS facility)
• Delivered (marked as delivered)

Tracking updates can take 24 to 72 hours to show up. Some shipments might not be tracked at all. This can happen if the envelope is too thick, the barcode is damaged, or it’s sorted by hand. In most cases, this doesn’t affect delivery.

If your shipment doesn't qualify for FCML

If an order doesn’t meet FCML rules by the time you need to ship, Whatnot will automatically upgrade the shipment to USPS Ground Advantage or Priority Mail.

Here's how it works: 

FAQs

Can I manually change FCML shipping method after a sale?

Yes. If for any reason you need to upgrade from First-Class Mail Letter to Ground Advantage or Priority Mail, just edit the shipment details and increase the weight of the package to 4 oz or more.

These upgrades count toward your weekly allowance of 5 free shipping adjustments. After that, fees may apply. 

When will I get paid for FCML orders?

First-Class Mail Letter is a special shipment type with limited tracking. Because of this, Whatnot doesn't wait for delivery scans to start processing your earnings.

Instead, your earnings begin processing:

• Standard payout: 10 days after you generate the label.
• Early Payout: Right after you generate the label.

Can I use FCML for other categories on Whatnot? 

FCML is only available for Trading Card Games, Sports Cards, and Stickers sold through live shows. We’re exploring if this shipping option can be expanded to other categories in the future.