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Transact Bridge allows merchants to change the plan associated with an existing subscription without creating a new subscription. A plan change can be used to:
  • Upgrade a customer to a higher-value plan.
  • Downgrade a customer to a lower-value plan.
  • Change the products or items included in the subscription.
  • Change the billing frequency associated with the plan.
  • Adjust the amount based on the unused portion of the current billing period.
When a plan is changed during an active billing period, the applicable adjustment can be calculated on a prorated, day-consumed basis. The prorate parameter in the subscription item configuration determines whether an item’s amount is partially calculated based on the days consumed.

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Upgrade Plan

An upgrade occurs when a customer moves from a lower-value plan to a higher-value plan. For example:
If the customer upgrades before the end of the current billing period, the unused portion of the current plan can be considered when calculating the amount applicable to the new plan.

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Upgrade Scenario

Consider a monthly prepaid subscription:
The customer has already consumed part of the Basic plan.
The unused portion of the Basic plan is considered for the applicable prorated credit. The credit can then be applied against the amount due for the Premium plan.

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Upgrade Flow

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Downgrade Plan

A downgrade occurs when a customer moves from a higher-value plan to a lower-value plan. For example:
If the customer changes the plan before the end of the current billing period, the applicable unused value of the existing Premium plan can be considered as a prorated credit. Because the new plan has a lower value, the resulting credit can be greater than the amount required for the new plan, depending on the timing and configured billing behavior.

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Downgrade Scenario

Consider:
The customer has consumed 15 days of the Premium plan and has 15 days remaining.
The unused Premium value can be calculated on the applicable prorated basis.
The applicable ₹1,000 represents the unused value of the existing Premium plan in this illustrative example.

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Downgrade Flow

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Prepaid Plan Change

For a prepaid subscription, the customer has already paid for the current service period. Therefore, when a plan change occurs before the current period ends:
  1. Determine the portion of the current plan already consumed.
  2. Determine the unused portion.
  3. Calculate the applicable prorated value of the unused portion.
  4. Apply the applicable credit toward the new plan.
  5. Continue the subscription using the new plan.

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Postpaid Plan Change

For a postpaid subscription, the customer uses the service during the billing period and payment is collected after billing. When the plan changes:
  1. The existing billing period and consumed usage are considered.
  2. The applicable amount is calculated for the current period.
  3. The new plan becomes applicable according to the subscription update.
  4. Subsequent usage is billed using the new plan configuration.
The proration mechanism can be used to calculate the applicable partial-period amount when the plan change occurs during a billing period.

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Upgrade vs Downgrade

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Credit Adjustment on a Prorated Basis

Proration adjusts subscription charges when a plan or service state changes before the current billing cycle ends. Instead of charging the full amount again, the system calculates the unused value of the current plan and the cost of the new plan or service period for the remaining days.
  • Day-based calculation: The prorate value on each subscription item enables TransactBridge to calculate the charge according to the number of days actually consumed.
  • Net payable: The customer pays only the difference when the new cost is higher than the unused credit.
  • Credit balance: When the unused value is higher, the balance can be added to the customer’s credit(which can be made visible on merchant dashboard) and later applied to another invoice, or shown separately, based on the merchant’s policy.
  • Billing anchor use case: When invoices are always generated on a fixed date, proration ensures that the initial partial period is billed fairly.
  • Pause/resume use case: The merchant may charge only for active days or create a prorated credit.
  • Upgrade/downgrade use case: The merchant can grant immediate access to the new plan and calculate the charge or credit for the remaining period.
For example: A monthly subscription is paused on the 15th and resumed on the 30th. Depending on the merchant’s policy, the customer may be charged only for the active days, or a credit may be created for the unused period.
This is handled by Transact Bridge

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Upgrade Example

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Downgrade Example

The examples above assume a 30-day billing period and a change exactly halfway through the billing period.

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PENDING UPDATES

Your customers may need to move between plans mid-cycle — add a product, remove one, or change a quantity/price on an active subscription. You do this with a single API call, sending the complete new list of items you want the subscription to have (not just what changed). TransactBridge has no separate “add-on” concept, so every plan change — bigger, smaller, or the same total value — is handled the same way, as an upgrade/downgrade. Because a plan change can increase what the customer owes, TransactBridge doesn’t switch the plan blindly. It first checks whether the change fits inside the payment authorization your customer already gave us:
  • Fits the existing authorization (or, for prepaid plans, no extra amount is owed) — the plan change applies immediately, in the same API call. No customer action needed.
  • Exceeds the existing authorization, or an extra payment is due right now (prepaid plans) — the change is held as a Pending Update. Your customer must complete a short checkout step — raising their payment authorization or paying the prorated difference — before the new plan takes effect.

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How proration works

Days already used in the current billing period are billed against the old items; days remaining in the period are billed against the new items. Your customer is never charged for the full new plan on a partial month, and never loses value for days already paid on the old plan.

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The same-day window

A Pending Update quotes prices — and, for cross-currency subscriptions, the FX rate — as of the moment it’s created. If your customer doesn’t finish checkout that same day, the Pending Update automatically expires at midnight India time (IST). It is not silently recalculated or retried later, since the quoted price/FX rate would be stale. You’ll need to call the update API again to restart the upgrade/downgrade.

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Integration steps

  1. Call Create Subscription API with subscriptionId and the full items array (name, quantity, amount, and — if your account requires product mapping — productReferenceId).
  2. Read the response:
    • updateFlag: true and mandateRequired: false — the plan change is already live.
    • mandateRequired: true — send your customer to redirectUrl (a hosted TransactBridge checkout page) to authorize the higher payment limit or pay the difference. If you use drop-in checkout, pass dropIn: true on the request to receive a token instead of a redirectUrl.
  3. Once your customer completes checkout, TransactBridge applies the new items to the subscription and sends you a webhook (callbackType: SUBSCRIPTION) carrying the updated subscription object.
  4. If your customer abandons checkout and doesn’t return before midnight IST, the Pending Update is discarded — call step 1 again to retry.
Optional flag: pass isCustomerRedirection: true on the update call to always send the customer through checkout, even when the change would otherwise apply instantly — useful if you want the customer to confirm coupon terms, or to force downgrades through a confirmation step.

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Lifecycle

An expired Pending Update is not retried automatically — call updateSubscription again to restart the upgrade/downgrade.

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Integration sequence

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Important Considerations

  • A plan upgrade or downgrade changes the plan associated with the existing subscription.
  • The prorate configuration controls whether an item’s amount is calculated on a partial, day-consumed basis.
  • For prepaid subscriptions, the unused portion of the already-paid period can be considered when calculating the applicable credit.
  • For postpaid subscriptions, the consumed portion of the billing period and applicable charges are considered when calculating the amount.
  • An upgrade generally results in an additional amount being payable when the new plan is more expensive.
  • A downgrade can result in a credit adjustment because the new plan has a lower value.
  • A prorated credit should not automatically be interpreted as a cash refund. The treatment of any resulting credit depends on the subscription update and billing configuration.
  • The exact amount depends on the plan amount, billing period, change date, applicable prorate configuration, and other subscription settings.
Proration basis: Transact Bridge documentation specifies that when an invoice needs to be partially paid, the total amount can be calculated using proration on a day-consumed basis.