Storage Plans

By purchasing enough iTunes Store gift cards to prepay a year's worth of charges. Aside from this, you can't; Apple no longer offers new annual plans.

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You cannot pay annually - Apple discontinued the annual plans some time ago. There are only the monthly subscriptions.

You can do as Neil suggests and preload your AppleID with a years worth of funds, but the subscription fee will still be deducted in monthly allotments, once per month. You simply can no longer pay for a year’s subscription in a single lump sum payment.