Customers fill their own box from your products and pay one box price: any 3 for a fixed price, 6 with 10% off, gift message included.
Tested on 2 buildsUpdated Nov 4, 2026Version 1.0.0CS-Cart, Multi-Vendor 4.17.2 – 4.21.x No core file edits
Built for
Build-a-Box Bundles: Customers fill their own box from your products and pay one box price1 of 8
What it does
For stores that sell gift boxes, snack and tea boxes, beauty sets, sock packs, movie or book bundles. The core Product bundles add-on sells a fixed set; here the customer chooses the contents. You pick a product as the box page, add sizes and their prices, point the box at categories or products, and the builder appears under the product block. Works on CS-Cart and Multi-Vendor, where vendors build boxes from their own products.
How it works
The shopper picks a size, adds products with Add and +/- buttons and watches the tray fill slot by slot with the regular total, the box price and the saving. The button unlocks when the box is full. In the cart each item shows its slot, the box line shows the gift message and an Edit box link. Changing the quantity of one line changes the whole box, removing one line removes the box. The server checks every box again before it enters the cart.
Features
Box builder under the product block of any product you choose
Box sizes with a fixed box price, a percent off the items or regular prices
Products from categories and subcategories, hand-picked products and exclusions
Category tabs, search, product cards with Add and +/- counters
Box tray with slots, progress, regular total, box price and saving
Repeat rules, maximum per product, stock-aware box quantities
Optional gift message in the cart, order pages and admin order
Exact cents per item line, so taxes, stock and payouts stay correct
Edit box from the cart, whole-box quantity and removal
Box report with top products, by box and by size
Vendor boxes on Multi-Vendor, storefront boxes on CS-Cart Ultimate
Full page cache safe on 4.21, works with responsive-based themes
What you get
Package
kv_build_a_box-1.0.0.zip, installed through Add-ons → Manage add-ons
Updates & support
12 months included. Download new versions from your account and install them in Add-ons → Manage add-ons or the Upgrade Center.
License
1 production installation. Staging, dev and localhost are free and unlimited. The add-on keeps working after the update period ends. How licensing works
Compatibility
We list only the builds we install and test on. “Tested” means the full test plan was run on that build; “Supported” means the build is inside the supported range and uses the same hooks.
CS-Cart version and edition compatibility
CS-Cart version
CS-Cart
CS-Cart Ultimate
Multi-Vendor
Multi-Vendor Ultimate
4.22 and later
Testing next
Testing next
Testing next
Testing next
4.21.2
Supported
Supported
Supported
Supported
4.20.x
Supported
Supported
Supported
Supported
4.19.x
Supported
Supported
Supported
Supported
4.18.x
Supported
Supported
Supported
Supported
4.17.2
Tested
Supported
Tested
Supported
Before 4.17.2
Not supported
Not supported
Not supported
Not supported
Last tested build: Multi-Vendor 4.17.2, Nov 4, 2026Tested on: Multi-Vendor 4.17.2, CS-Cart 4.17.2
Requirements
Platform
CS-Cart and Multi-Vendor 4.17.2 or later
Requirement
Administrator access to the store's admin panel
Core changes
None. Hooks and template overrides only
1.0.0
Nov 4, 2026
Latest
Added 7
Box builder on a chosen box page: box sizes, product grid with category tabs and search, box tray with slots, regular total, box price and saving, mobile bottom bar.
Box prices per size: fixed price, percent off the items or regular prices, split over the item lines to the cent.
Tested on Multi-Vendor 4.17.2, CS-Cart 4.17.2. First release.
Can a box mix products of different vendors?
No. On Multi-Vendor a box holds products of the box page's vendor, so it ships as one suborder.
Why does a product not appear in the builder?
It has product options, it is disabled or hidden, it is out of stock while "Hide products that are out of stock" is on, it is excluded, it belongs to another vendor, or it is the box page of another box. The builder lists at most the number set in "Products per builder".
Do coupons work with boxes?
Yes. Cart promotions and coupons apply to the order as usual. Catalog promotions with conditions do not reduce box items again, because the box price is the discount.
How are taxes calculated?
Each item line keeps its own product and tax class; only its price is the share of the box price. The shares add up exactly to the box price.
What happens to boxes in carts when I change a box?
Their lines go back to regular prices and the cart shows that the box changed. Customers can use "Edit box" to fill it again.
Does it work with the full page cache of CS-Cart 4.21?
Yes. The builder is the same for every visitor; the selection lives in the browser.
Can customers buy the box page product alone?
No. Its normal buy button is replaced by "Fill your box"; posting it alone shows "Choose the items of your box first".