A cart offer takes one deposit for the whole order. With a fixed amount, the buyer pays that amount once, whatever is in their basket.
Where to find it
Depositly → Purchase options → Cart page → Create purchase option
How to set it up
Go to Purchase options and switch to Cart page.
Click Create purchase option.
On Offer terms, click Create in draft-order mode (or switch the offer to draft-order mode).
Set the deposit type to Fixed amount and enter the amount.
Choose the balance due date. If buyers pay in person, turn on Take the balance in person on collection.
On Where it applies, leave it on the whole order, or pick the products that should trigger the deposit.
Set it to Active and click Save.
Why draft-order mode?
In automatic mode, Shopify takes a fixed deposit once for every item in the cart, not once for the order. The app won't let you save a fixed cart deposit in automatic mode for this reason. Draft-order mode takes one fixed amount per order. A percentage deposit works in either mode.
Good to know
If the cart has at least one covered product, the whole basket becomes one deposit order. Regular items in the same cart are paid with the balance. If you want pre-orders and regular orders kept apart, tell buyers to place them as separate orders.
Only one cart offer can be live at a time.