Here’s a very simple snippet that achieves a very complex task – what if you wanted to force your Cart to charge a deposit or a fixed fee, no matter the product price?
Well, thankfully WooCommerce is pretty flexible and a lot of workarounds can be found. In this case, forcing the checkout to a fixed amount (e.g. $100) is as simple as applying a negative “cart fee” to make the total become $100.
Sounds like Japanese? Great – here’s why you’re on Business Bloomer. Copy the snippet, apply it to your test WooCommerce site and see the magic happen – without knowing anything about coding!

PHP Snippet: Force Cart to Specific Amount (Deposit) – WooCommerce
/** * @snippet Force Cart to Specific Amount (Deposit) - WooCommerce * @how-to Get tutoraspire.com FREE * @sourcecode https://tutoraspire.com/?p=72625 * @author Tutor Aspire * @testedwith WooCommerce 3.5.1 */ // Note: this will force Cart to $100 add_action( 'woocommerce_cart_calculate_fees','tutoraspire_force_cart_to_100' ); function tutoraspire_force_cart_to_100() { $total_minus_100 = WC()->cart->get_cart_contents_total() - 100; WC()->cart->add_fee( 'Adjustment', $total_minus_100 * -1 ); }