Pokemon TCGbulk is one of the few downsides to the hobby. However, by selling your bulk you can make some of your money back to purchase more packs in the future.
Most retailers that offer to buy your bulk have common conditions to be met, including a near mint card condition and general organization of your bulk into common, uncommon, rare etc.

Some retailers offer a payout and/or store credit when buying your bulk, so you can decide which method is better to fund your futurePokemon TCGpurchases.
Where to Sell Your Pokemon Bulk
Troll and Toad
This is a fairly popular site used in the United States to sell bulk to. The site also offers bulk to buy fromPokemon TCG,Yu-Gi-Oh,Magic the Gatheringand more.
Troll and Toad also offers a 35% bonus.

Safari Zone Collectibles
Safari Zone offers payouts as well as store credit, both at the same rates.
There is also no limit to the amount of bulk you can send in. The Safari Zone website offers a submission form to register your bulk.

Safari Zone
The Colosseum
The Colosseum accepts all cards except for energy and championship style cards.
The application form on the website details the price for each accepted card.

Pika Shop offers payouts plus store credit, accepting commons, uncommons, trainer cards, holos and reverse holos.
This store also offers free postage.
Puca Puca Games
£10 PayPal or £15 Store Credit per 1000 Common/Uncommon/Non-Holo Rare/Trainers
£1 PayPal or £1.50 Store Credit per 10 Reverse Hollow Common/Uncommon/Trainers

£3 PayPal or £4.50 Store Credit per 10 Reverse Hollow Rares
Puca Puca Games also offers pre-paid shipping labels.
Chase Games
Chase Games accepts older energy cards for 1p per card all the up to £3 for Amazing Rares and SV Cards.
Note: Chase Games only offers store credit.
Alternative Options to Sell your Pokemon Bulk
You can also register your cards on the TCGplayer Marketplace, however this option will take more time.
Facebook Groups
Members of variousPokemon TCGFacebook groups are always on the hunt for card bulk, and you can choose to either sell your cards separately or in one haul.
It is recommended that you only join Facebook groups that are monitored by the administrator, who only entertain genuine buyers and sellers.