Your "Asset Account" is a combination of multiple things: your AutoBuy, Stored Ammo, and Pending Inventory. When you delete an Asset Account you are actually canceling all of those things.
There are a few reasons why you would actually need to delete an Asset Account. Instead, you can change the budget, add calibers, or remove calibers instead of deleting it. You can also simply "Skip" an auto-buy if you don't want it to run for an extended period of time as well.
If you do need to delete an Asset Account, however, the process is relatively simple. Just navigate to the Asset Account you want to remove. select the trash can on the right.
Next, you will receive a summary with the amount that will be refunded as a credit to your account.
Here is what that looks like:
Once you click the "Cancel My Asset Account Now" confirmation button on the bottom your assets will immediately be sold and you will receive the account credits.
One final note: this action is permanent, so use it wisely.
If you want to leave AmmoSquared completely, you'll need to request a Cash Out Refund.