If you have run out of credits completely (don't forget our very fair 'fair usage' policy), you can manually renew or change your subscription early and receive the months credits straight away or you can make a once off purchase of credits in bulk without affecting your subscription.
For example, if your subscription date is on the 1st of the month and the credits run out on the 20th, you can renew or change your subscription on the 20th and the monthly billing then occurs on the 20th of the month going forward.
To renew or change your subscription click on the user drop down top right and select Account Settings:
Under the Subscription and Billing tab, click on 'Change Subscription'
To ensure your credits are added and your new subscription kicks in straight away, you want to ensure you select the renew now option. You can then select the level of subscription required and click Change. The same level is treated as a straight renewal or you can upgrade if the larger subscription if required. When manually changing subscription, you can also choose to keep your current renewal date so if you were changing to a higher or lower subscription, the subscription would change to this new selection on your normal renewal date
You can also select the purchase credits in bulk option where you just add in the number you want to buy and make your purchase. The credits are added straight away and your subscription is not affected. Please note that the cost of buying credits in bulk is slightly more expensive than the cost of a credit when you purchase a subscription