Delete Payments

Is this in a dev site or a live site?

Commerce Purchase Order uses the standard Commerce Payment entity and therefore its data is stored in the commerce_payment table. In my experience, payments are tied to orders, and are normally voided. There is a delete path defined in the Payment entity, /admin/commerce/orders/{commerce_order}/payments/{commerce_payment}/delete which also communicates that this is tied to the order.

You could delete all such payments via a query on that table for payments with type payment_purchase_order but I'm not sure what that would do to your orders.

I'm not sure what version of Commerce you are using, but I see a Delete operation added as an additional action in \Drupal\commerce_payment\PaymentListBuilder::getDefaultOperations which is also tied to orders by the route entity.commerce_payment.collection. I'm transferring this request upstream since it seems to be about Payments generally.

Although this might deviate somewhat from the OP report, I will pick up the thread from #6. As of this time, one cannot delete payments in Commerce 2 except in certain circumstances due to \Drupal\commerce_payment\PaymentAccessControlHandler, which does this check on the delete op:

    if ($operation == 'delete') {
      // @todo Add a payment gateway method for this check,
      // to allow a differently named test mode.
      $access = $access->andIf(AccessResult::allowedIf($entity->getPaymentGatewayMode() == 'test'));
    }

While this may make total sense where an external payment vendor is involved, our use case involves custom payments that represent offline transactions and that have legitimate need to be deleted on some occasions; Our custom gateways do not use the mode field, and wouldn't be set to "test" at any rate, so the access check fails. As indicated in the @todo, we should have the ability to decide when a payment can be deleted via our own gateway definitions.

Clearly this will require some work, not only to invoke the gateway when doing the access check, but to implement payment method cleanup on the payment delete event and possibly changing certain gateway & payment data on the order when these are removed (unless PaymentOrderUpdater handles that – regardless, making sure we don't end up with inconsistent data after deletion.)

Changing this line to:
$access = $access->andIf(AccessResult::allowedIf($entity->getPaymentGatewayMode() != 'live'));

At least lets you delete manual payments.

Here's an idea.

Opened a separate smaller issue specifically for manual payments.

#3379407: Allow deleting manual payments through the UI.