diff --git a/src/Plugin/Action/CreateAdjustmentAction.php b/src/Plugin/Action/CreateAdjustmentAction.php
new file mode 100644
index 0000000000000000000000000000000000000000..fd86b6e8b0ef658b72a999baed2c0e1467b88242
--- /dev/null
+++ b/src/Plugin/Action/CreateAdjustmentAction.php
@@ -0,0 +1,234 @@
+<?php
+
+namespace Drupal\eca_commerce\Plugin\Action;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Session\AccountInterface;
+use Drupal\commerce_order\Adjustment;
+use Drupal\commerce_order\AdjustmentTypeManager;
+use Drupal\commerce_order\EntityAdjustableInterface;
+use Drupal\commerce_price\Price;
+use Drupal\commerce_store\Resolver\StoreResolverInterface;
+use Drupal\eca\Plugin\Action\ConfigurableActionBase;
+use Drupal\eca\Plugin\ECA\PluginFormTrait;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+/**
+ * Describes the eca_commerce add_adjustment action.
+ *
+ * This allows users to add price adjustments when added to cart based on ECA.
+ *
+ * @Action(
+ * id = "eca_commerce_add_adjustment",
+ * label = @Translation("Order Item: Add Price Adjustment"),
+ * eca_version_introduced = "1.0.0",
+ * type = "commerce_order_item"
+ * )
+ */
+class CreateAdjustmentAction extends ConfigurableActionBase {
+
+ use CurrencyActionTrait;
+ use PluginFormTrait;
+
+ /**
+ * The adjustment type manager.
+ *
+ * @var \Drupal\commerce_order\AdjustmentTypeManager|null
+ */
+ protected ?AdjustmentTypeManager $adjustmentTypeManager;
+
+ /**
+ * The default store resolver.
+ *
+ * @var \Drupal\commerce_store\Resolver\StoreResolverInterface|null
+ */
+ protected ?StoreResolverInterface $defaultStoreResolver;
+
+ /**
+ * {@inheritdoc}
+ */
+ public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition): static {
+ $instance = parent::create($container, $configuration, $plugin_id, $plugin_definition);
+ $instance->adjustmentTypeManager = $container->get('plugin.manager.commerce_adjustment_type', ContainerInterface::NULL_ON_INVALID_REFERENCE);
+ $instance->defaultStoreResolver = $container->get('commerce_store.default_store_resolver', ContainerInterface::NULL_ON_INVALID_REFERENCE);
+ return $instance;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function access($object, ?AccountInterface $account = NULL, $return_as_object = FALSE) {
+ $access_result = AccessResult::AllowedIf($object instanceof EntityAdjustableInterface);
+
+ return $return_as_object ? $access_result : $access_result->isAllowed();
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function execute(mixed $entity = NULL): void {
+ if (!class_exists(Adjustment::class) || !class_exists(Price::class)) {
+ // Early return.
+ return;
+ }
+
+ $label = $this->tokenService->replaceClear($this->configuration['label']);
+ $amount = $this->tokenService->replaceClear($this->configuration['amount']);
+ $fallback_currency = $this->getFallbackCurrency($entity);
+ $currency = $this->configuration['currency'] ?: $fallback_currency;
+ if ($currency === '_eca_token') {
+ $currency = $this->getTokenValue('currency', $fallback_currency);
+ }
+ $percentage = $this->tokenService->replaceClear($this->configuration['percentage']);
+ $definition = [
+ 'type' => $this->configuration['type'],
+ 'label' => $label,
+ 'amount' => new Price($amount, $currency),
+ 'percentage' => $percentage ?: NULL,
+ 'source_id' => 'custom',
+ 'included' => $this->configuration['included'],
+ 'locked' => $this->configuration['locked'],
+ ];
+ $adjustment = new Adjustment($definition);
+ switch ($this->configuration['method']) {
+ case 'set:clear':
+ $entity->setAdjustments([]);
+
+ case 'append:drop_first':
+ $entity->addAdjustment($adjustment);
+ break;
+ }
+
+ if ($this->configuration['save_entity']) {
+ $entity->save();
+ }
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function defaultConfiguration(): array {
+ return [
+ 'method' => 'set:clear',
+ 'type' => '_none',
+ 'label' => '',
+ 'amount' => '',
+ 'currency' => '',
+ 'percentage' => '',
+ 'included' => FALSE,
+ 'locked' => TRUE,
+ 'save_entity' => FALSE,
+ ] + parent::defaultConfiguration();
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function buildConfigurationForm(array $form, FormStateInterface $form_state): array {
+ $form['method'] = [
+ '#type' => 'select',
+ '#title' => $this->t('Method'),
+ '#default_value' => $this->configuration['method'],
+ '#description' => $this->t('The method to set an entity, like cleaning the old one, etc..'),
+ '#weight' => -40,
+ '#options' => [
+ 'set:clear' => $this->t('Set and clear previous value'),
+ 'append:drop_first' => $this->t('Append and drop first when full'),
+ ],
+ ];
+ $types = [
+ '_none' => $this->t('- Select -'),
+ ];
+ if (isset($this->adjustmentTypeManager)) {
+ foreach ($this->adjustmentTypeManager->getDefinitions() as $id => $definition) {
+ if (!empty($definition['has_ui'])) {
+ $types[$id] = $definition['label'];
+ }
+ }
+ }
+ $form['type'] = [
+ '#type' => 'select',
+ '#title' => $this->t('Type'),
+ '#options' => $types,
+ '#weight' => 1,
+ '#default_value' => $this->configuration['type'],
+ '#required' => TRUE,
+ ];
+ $form['locked'] = [
+ '#type' => 'checkbox',
+ '#title' => $this->t('Locked'),
+ '#description' => $this->t('Note: Adjustments added from UI interactions need to be locked to persist after an order refresh.'),
+ '#default_value' => $this->configuration['locked'],
+ ];
+ $form['label'] = [
+ '#type' => 'textfield',
+ '#title' => $this->t('Label'),
+ '#size' => 20,
+ '#default_value' => $this->configuration['label'],
+ '#required' => TRUE,
+ '#eca_token_replacement' => TRUE,
+ ];
+ $form['amount'] = [
+ '#type' => 'number',
+ '#title' => $this->t('Amount'),
+ '#default_value' => $this->configuration['amount'],
+ '#required' => TRUE,
+ '#attributes' => ['class' => ['clearfix']],
+ '#eca_token_replacement' => TRUE,
+ ];
+ $form['currency'] = [
+ '#type' => 'select',
+ '#title' => $this->t('Currency'),
+ '#options' => ['_none' => 'Use default'] + $this->getAvailableCurrencies(),
+ '#default_value' => $this->configuration['currency'],
+ '#size' => 5,
+ '#required' => TRUE,
+ '#eca_token_select_option' => TRUE,
+ ];
+ $form['percentage'] = [
+ '#type' => 'number',
+ '#title' => $this->t('Percentage'),
+ '#default_value' => $this->configuration['percentage'],
+ '#attributes' => ['class' => ['clearfix']],
+ '#eca_token_replacement' => TRUE,
+ ];
+ $form['included'] = [
+ '#type' => 'checkbox',
+ '#title' => $this->t('Included in the base price'),
+ '#default_value' => $this->configuration['amount'],
+ ];
+ $form['save_entity'] = [
+ '#type' => 'checkbox',
+ '#title' => $this->t('Save entity'),
+ '#default_value' => $this->configuration['save_entity'],
+ '#description' => $this->t('Saves the entity or not after setting the value.'),
+ '#weight' => -10,
+ ];
+
+ return parent::buildConfigurationForm($form, $form_state);
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function submitConfigurationForm(array &$form, FormStateInterface $form_state): void {
+ $this->configuration['method'] = $form_state->getValue('method');
+ $this->configuration['type'] = $form_state->getValue('type');
+ $this->configuration['locked'] = $form_state->getValue('locked');
+ $this->configuration['label'] = $form_state->getValue('label');
+ $this->configuration['amount'] = $form_state->getValue('amount');
+ if ($form_state->getValue('currency') === '_none') {
+ $currency = '';
+ }
+ else {
+ $currency = $form_state->getValue('currency');
+ }
+ $this->configuration['currency'] = $currency;
+ $this->configuration['percentage'] = $form_state->getValue('percentage');
+ $this->configuration['included'] = $form_state->getValue('included');
+ $this->configuration['save_entity'] = $form_state->getValue('save_entity');
+ parent::submitConfigurationForm($form, $form_state);
+ }
+
+}
diff --git a/src/Plugin/Action/CurrencyActionTrait.php b/src/Plugin/Action/CurrencyActionTrait.php
new file mode 100644
index 0000000000000000000000000000000000000000..348751de67ac9af42f8c8669680a889ad5dd20b7
--- /dev/null
+++ b/src/Plugin/Action/CurrencyActionTrait.php
@@ -0,0 +1,86 @@
+<?php
+
+namespace Drupal\eca_commerce\Plugin\Action;
+
+use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\commerce_order\Entity\OrderItemInterface;
+use Drupal\commerce_store\Entity\EntityStoreInterface;
+use Drupal\commerce_store\Entity\StoreInterface;
+use Drupal\commerce_store\Resolver\StoreResolverInterface;
+
+/**
+ * Trait for resolving the default currency to use for a price adjustment.
+ */
+trait CurrencyActionTrait {
+
+ /**
+ * The entity type manager service.
+ *
+ * @var \Drupal\Core\Entity\EntityTypeManagerInterface
+ */
+ protected EntityTypeManagerInterface $entityTypeManager;
+
+ /**
+ * The default store resolver.
+ *
+ * @var \Drupal\commerce_store\Resolver\StoreResolverInterface|null
+ */
+ protected ?StoreResolverInterface $defaultStoreResolver;
+
+ /**
+ * Gets all available currencies configured on the site.
+ *
+ * Ensures format is compatible with currency select form element.
+ *
+ * @return array
+ * Array of currency codes with both keys and values populated. For example,
+ * @code
+ * ['USD' => 'USD']
+ * @endcode
+ */
+ protected function getAvailableCurrencies(): array {
+ $currencies = $this->entityTypeManager->getStorage('commerce_currency')->loadMultiple();
+ $currency_codes = array_keys($currencies);
+ return array_combine($currency_codes, $currency_codes);
+ }
+
+ /**
+ * Gets the default currency to use if the action was not configured with one.
+ *
+ * @param mixed $entity
+ * The entity used as a reference e.g. Order, Order Item.
+ * The currency of the entity's total price is used if available.
+ * Otherwise, the default currency of the respective Store is used.
+ *
+ * @return string
+ * The default currency.
+ */
+ protected function getFallbackCurrency(mixed $entity = NULL): string {
+ return $entity?->getTotalPrice()?->getCurrencyCode()
+ ?? $this->getFallbackStore($entity)?->getDefaultCurrencyCode()
+ ?? 'USD';
+ }
+
+ /**
+ * Gets the given Order or Order Item entity's associated Store.
+ *
+ * Otherwise return the default Store.
+ *
+ * @param mixed $entity
+ * The entity used as a reference e.g. Order, Order Item.
+ *
+ * @return \Drupal\commerce_store\Entity\StoreInterface|null
+ * The respective Store.
+ */
+ protected function getFallbackStore(mixed $entity = NULL) : ?StoreInterface {
+ if ($entity instanceof EntityStoreInterface) {
+ $store = $entity->getStore();
+ }
+ elseif ($entity instanceof OrderItemInterface) {
+ $store = $entity->getOrder()?->getStore();
+ }
+ $store ??= $this->defaultStoreResolver?->resolve();
+ return $store;
+ }
+
+}