When processing transactions, the transaction type and transaction class parameters determine the action and category applied to the transaction. Below are the available options for both:

The available options are:

Transaction Type	Description
auth	Seek authorisation from the card issuer for the amount specified. If authorised the funds will be reserved but will not be debited until such time as a corresponding capture command is made. This is sometimes known as pre-authorisation.
capture	Debit the funds that have been reserved on a card using a previous auth transaction. The amount that to be captured can be any amount up to the full amount of the initial auth. It cannot exceed the initial amount. This is sometimes known as post-authorisation or as pre-authorisation completion.
release	Release funds that had previously been reserved using an auth transaction. It is possible for the amount that is captured to be lower than the initial auth amount. In this case the remaining balance should be released back to the card holder. A release transaction cannot be voided. The full amount of the auth can be released in order to cancel the transaction. A release cannot be done on any transaction type other than an auth.
sale	Immediate purchase request. This has the same effect as would be had by performing an auth transaction followed by a capture transaction for the full amount. No additional capture stage is required.
refund	Credit the amount specified back to the card holder. A refund can be processed against a sale or capture transaction.
void	Cancel a sale, refund. Voiding a transaction prevents the funds from being captured or finalized. This action is typically only available within a limited time window (usually a few hours) after the original transaction.
verify	Confirm that the card details given are valid. No funds are reserved or taken from the card. Note: Please contact support at 'support@telr.com' to enable zero auth verify transaction on your store.

Transaction Class	Description
moto	Process as Mail Order / Telephone Order.
ecom	Process as an Internet based E-Commerce transaction. The use of 3-D Secure is mandatory for this class of transaction.
cont	"Process as a continuous authority transaction for example a recurring subscription."

For E-Commerce transactions it is mandatory that you also implement 3-D Secure as part of the authorisation process. The payment gateway provides remote access to an MPI which will simplify this process for you. See the section on 3-D Secure for further reference.

For items or services that have an immediate delivery, the sale transaction method is often the simplest one to use. If there can be a delay between the transaction and eventual shipping of the goods, then separate auth and capture transactions should be used. You must ensure that you perform the capture stage of the transaction otherwise the funds will not be taken from the card and you will not receive payment. You should process the capture request before actually shipping the goods to ensure that the card used is still valid.