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Letter add-ons
Letter add-ons are features exclusive to our Enterprise tier customers. Upgrade to the appropriate Print & Mail edition to gain access, or contact our sales team to learn more.
Letter envelopes can be customized with branding, artwork, or messaging to communicate vital information to your recipients even before they open the envelope. Lob offers limited customization for some envelopes, including standard #10 outer envelopes (single-windowed) and #9 return envelopes (no window / single-windowed options).
Paper cards can now be affixed to letters, providing a compelling method to direct customers to special promotions and drive engagement, both online and in-store. Having “faux” cards can serve as a tangible and memorable reminder for any upcoming marketing promotion.
To get started with letters with card affix, check out our API documentation or visit our Template Gallery for inspiration.
Paper cards can only be affixed horizontally to the top fold of a tri-folded letter, and to the face letter on the first page.
Reference our layout templates on where to place your design elements on the card, and the location of where the card will be affixed to any given letter.
Artwork can be featured on both sides of the card. In general, any critical design elements or text should be 0.125" away from the final trim line due to movement at press. There are also no color limitations for cards. Other considerations are:
- Double-check that all images are embedded into your document
- Ensure all rasterized artwork (images, effects, copy, etc.) is created and saved at or above 300 dpi
- Thin, small fonts with over 3 colors may fill in slightly or appear “fuzzy”
- Line weights of 0.5 pt or more assure optimum print results
- Any barcodes/QR codes provided need to be print-ready
- CMYK document
Cards must be created, ordered, and printed, and available in your inventory before they can be utilized.
Upload your front and back designs to create a new card, then order inventory for your card. Cards can be purchased as a one-off order or through auto-reordering.
- Allow an estimated 20 business days for cards to be available for use in your Lob dashboard.
- The minimum order quantity is 10,000 cards per artwork design submitted.
- Spoilage is an industry norm that occurs during print set-up and processing. Based on the industry average, we recommend adding 2-3% to account for spoilage.
- Upload a front and back design, and hit Create
- Once card details show, select the Order button at the bottom
- Add the desired number of cards and hit Order
Description (Required, string)
: A name to identify your cardFront (Required, string)
: A locally hosted PDF or hosted PDF URL for the front card artworkBack (Optional, string)
: A locally hosted PDF or hosted PDF URL for the back card artwork
Quantity (Required, number)
: Number of cards you would like to order
Timing and delivery is dependent on order size and complexity, and may be additionally delayed by forces outside of Lob's control (e.g. USPS delays, printer site shutdowns due to Covid, paper shortages, extreme weather events).
Once cards are ordered, they cannot be sent with letters until your Lob dashboard indicates they are fully stocked and available in your inventory. An email will notify you once your cards are in stock and are ready to be sent with letter campaigns.
The minimum send quantity is 5,000 cards per letter campaign. If a letter campaign is created with a specified card ID that is not in stock, the request will be rejected. Affixing charges will be billed with each Letter API call made, which is separate from the initial card order.
Special considerations when sending card-affixed letters:
- Letters with card affix are limited to a single sheet at max (can be double-sided)
- Cards can only be affixed horizontally to the top fold of a tri-folded letter, and to the face letter on the first page
- Card-affixed letters will be sent in a standard #10 double-windowed envelope
- Card-affixed letters cannot be sent with custom envelopes or buckslips at this time
- Card-affixed letters cannot be used with Certified or Registered Mail at this time
In “Configure Settings” Step 1 of the Campaigns Letter creation flow, choose “Card” as your add-on
In “Choose Creative” Step 3 of your Campaign, select the card design that you’d like to use in your Letter campaign.
- You cannot send cards if you have an insufficient amount in your inventory, as your campaign request will be rejected
- You cannot pair cards with other letter add-ons at this time
- When loading your creative assets, set the
details[cards][0]
parameter in yourPOST
call tohttps://api.lob.com/v1/creatives
to the desiredcard_id
. The cards parameter is an array which accepts a singlecard_id
. - In the future, we may begin accepting multiple
card_id
s, hence the array data type.
Additionally, you can find all cards in your account by sending a
GET
call to https://api.lob.com/v1/cards
Affixing cards to letters can be done via the single-endpoint Letters API, similar to Custom Envelopes
- Set the cards parameter in your
POST
call tohttps://api.lob.com/v1/letters
to the desired card ID, which is found in your Lob dashboard - Additionally, you can find all cards in your account by sending a
GET
call tohttps://api.lob.com/v1/cards
When using the Letters API single endpoint (
https://api.lob.com/v1/letters)
, cards must be sent in groups of at least 5,000 card-affix letter API requests during any 24-hour print-day period from 10AM PT to 10AM PT. If you do not, you may incur setup costs of $250/day on your monthly usage invoice. Reach out to your dedicated Customer Success Manager if you have questions.Currently we do provide the following card affix offering:
- Cards affixed to letters (one sheet total, front-side only)
- Static, non-personalized artwork designs for paper cards
- Horizontal card orientation in a single size
- Cards affixed to the top fold of a trifold letter towards the right
- Letters sent in standard #10 outer envelopes
We do not support the following offerings:
- Cards affixed to any other mail format (e.g. self-mailers)
- Cards affixed to letters that totals more than a single page, or on the back-side
- Dynamic, personalized artwork designs that are unique to the recipient
- Plastic cards (e.g. credit or loyalty cards)
- Vertical card orientation or different card sizes
- Cards affixed to any desired location on a letter
- Letters sent in customized #10 outer envelopes
- Card affix for Registered or Certified letters
Buckslips are small mail inserts that can be sent with letters to improve your ROI on marketing campaigns. These attention-grabbers can add pops of color in an otherwise plain-looking letter, and combined with compelling promotions, can be a very cost-effective solution to boost your response rates.
Buckslips can be sent through Campaigns API or the Campaigns dashboard, but NOT through the single-endpoint Letter API. To get started with buckslips, check out our:
- Or watch a quick demo of ordering buckslips and sending them with letters via the dashboard
Artwork can be featured on both sides of the buckslip. In general, any critical design elements or text should be 0.125" away from the final trim line due to movement at press. There are also no color limitations for buckslips.
Other considerations are:
- Double-check that all images are embedded into your document
- Ensure all rasterized artwork (images, effects, copy, etc.) is created and saved at or above 300 dpi
- Thin, small fonts with over 3 colors may fill in slightly or appear “fuzzy”
- Line weights of 0.5 pt or more assure optimum print results
- Any barcodes/QR codes provided need to be print-ready
Buckslips must be created, ordered, and printed, and available in your inventory before they can be utilized.
Upload your front and back designs to create a new buckslip, then order your inventory. . Buckslips can be purchased as an one-off order or through auto-reordering.
- The minimum order quantity is 10,000 buckslips per artwork design submitted
- Allow an estimated 10 business days for buckslips to be available for use in your Lob dashboard.
- Spoilage is an industry norm that occurs during print set-up and processing. Based on the industry average, we recommend adding 2-3% to account for spoilage.
- Upload a front and back design, and hit Create
- Once buckslip details show, select the Order button at the bottom
- Add the desired number of buckslips and hit Order
Description (Required, string)
: A name to identify your buckslipFront (Required, string)
: A locally hosted PDF or hosted PDF URL for the front buckslip artworkBack (Optional, string)
: A locally hosted PDF or hosted PDF URL for the back buckslip artwork
Quantity (Required, number)
: Number of buckslips you would like to order
Once buckslips are ordered, they cannot be sent with letters until your Lob dashboard reflects they are fully stocked and available in your inventory. An email will notify you once your buckslips are in stock and are ready to be sent with letter campaigns.
The minimum send quantity is 5,000 buckslips per letter campaign. If a letter campaign is created with a specified buckslip ID that is not in stock, the campaign request will fail.
Special considerations for sending letters with buckslips:
- Only 1 buckslip max per letter request
- Buckslips counts as one sheet in a letter
- Any letter including a buckslip can have a maximum total of 6 sheets (5 letter sheets + 1 buckslip) to fit in a #10 standard envelope
- Said another way, a buckslip cannot be inserted in letters over 6 sheets, as it cannot be inserted in a flat envelope at this time
- Custom envelopes (outer & return envelopes) are supported for letters with buckslips
- Buckslips cannot be sent with card-affixed letters at this time
- Buckslips cannot be used with Certified or Registered Mail at this time
- Buckslips cannot be sent using the single endpoint Letters API at this time
- In “Configure Settings” Step 1 of the Campaigns Letter creation flow, choose “Buckslip” as your add-on
- In “Choose Creative” Step 3 of your Campaign, select the buckslip design that you’d like to use in your Letter campaign.
- You cannot send buckslips if you have an insufficient amount in your inventory, as your campaign request will be rejected
- When loading your creative assets, set the
details[buckslips][0]
parameter in yourPOST
call tohttps://api.lob.com/v1/creatives
to the desiredbuckslip_id
- The
buckslips
parameter is an array which accepts a singlebuckslip_id
- In the future, we may begin accepting multiple
buckslip_id
’s, hence the array data type
- Additionally, you can find all buckslips in your account by sending a
GET
call tohttps://api.lob.com/v1/buckslips

What your inventory management screen typically looks like (Envelope inventory in this example)
Depending on the custom mail type selected, you will see some of the following details of your ordered design:
- Design
- Size
- Type
- Finish
View the number of remaining custom items in your inventory and the number of orders that are still outstanding or fulfilled. Inventory statuses include:
- Available: Inventory currently in stock and ready to use
- Reserved: Inventory allocated for scheduled campaigns
- Remaining: Inventory available, less reserved inventory
Inventory for custom items will decrement as you send letters with the add-on item of a specific design, and increment if you cancel a letter request. It may take a few minutes for the inventory quantity to update after any action.
Alternatively, use a
GET
call to the item endpoint to return a list of all items on your account, and any available and pending inventory.- Buckslips:
https://api.lob.com/v1/buckslips
- Cards:
https://api.lob.com/v1/cards
- Envelopes:
https://api.lob.com/v1/envelopes
Accurate inventory management is essential for ensuring that we have the right products available to meet our customers' needs. Lob has automated tools and physical audits in place for regularly reconciling inventory, but we need to account for product spoilage.
We are focused on addressing routine product spoilage that occurs during print set-up and assembly: Mailpieces generated during setup and testing are discarded along with any misprints or damaged pieces. For items printed on demand, this is not an issue, but for orders using pre-printed custom inventory, this ultimately impacts the accuracy of Lob's reported inventory.
By addressing this issue and accounting for spoilage at the time of processing, we can improve the timeliness and accuracy of our inventory, to the benefit of your mail campaigns.
- An auto-triggered overnight job will calculate spoilage from the previous production day and Lob will decrement it from your inventory accordingly.
- As a proactive measure, based on the industry average, we recommend adding 2-3% to account for spoilage when ordering custom inventory (custom envelopes, cards, buckslips).

Sample spoilage message when ordering
By addressing this issue and accounting for spoilage, we can improve the timeliness and accuracy of our inventory, to the benefit of your mail campaigns.
Given add-on items require additional lead times for printing and stocking in inventory, we recommend enabling auto-reordering for any items that will be continuously utilized to ensure there will be no risk of running out. When reordering is turned on, a new order will be submitted whenever the remaining inventory quantity falls below 20%. A confirmation will show the reorder quantity and price that will be charged.
- To turn on auto-reordering:
- Select the design you would like to auto-reorder
- Go to the Auto-Reorder Settings section, click Set Up, set auto-reorder to on, and hit Save
- Add a reorder quantity, the number of items to be ordered when your most recent order falls below 20% of the original order quantity, and hit Save
- To turn off auto-reordering:
- Go into the same Auto-Reorder Settings
- Set the auto-reorder button to off, and hit Save
Order details for any particular item design will be populated in the order history window once submitted, including order date, item ID, order quantity, inventory status, and expected availability date.
- Order status: Provides current item status
- Pending: Lob is reviewing the order submission
- In Production: The order is being fulfilled
- Available: Item is available in inventory and ready for use
- Expired: For envelopes only; indicates if envelopes expired (after 6mo)
- Canceled: Customer canceled order while status was pending
- Estimated date: Lob’s rough estimation of when items may be available in your inventory. However, an email confirmation will be sent when they are actually ready for use.
- Expand details: Each order under a specific design can be expanded by clicking on the ‘+’ sign to the right in each row, where the expiration date (envelopes only), unit price, and total order cost will become visible
Last modified 4mo ago