In Hedera Services 0.16.1, we are excited to announce support for HIP-18 (Custom Hedera Token Service Fees).
Hedera tokens can now be created with a schedule of up to 10 custom fees, which are either fixed in units of ℏ or another token; or fractional and computed in the units of the owning token. The ledger automatically charges custom fees to accounts as they send units of a fungible token (or ownership of a NFT, see below) via a CryptoTransfer.
When a custom fee cannot be charged, the CryptoTransfer fails atomically, changing no balances other than for the Hedera network fees.
The five case studies in this document show the basics of how custom fees are charged, and how they appear in records. Note that at most two "levels" of custom HTS fees are allowed, and custom fee charging cannot require changing more than 20 account balances.
⚠️ There is one variation on custom fees that requires a work-around in this release. Specifically, if a fixed fee should be collected in the units of the "parent" token to whose schedule it belongs, then in Release 0.16.0 this must be accomplished using a FractionalFee as described in this issue. In Release 0.17.0 the more natural FixedFee configuration will be available.
In this release we have also enabled previewnet support for HIP-17 (Non-fungible Tokens). Unique token types and minted NFTs are more natural for many use cases than fungible token types. The Hedera Token Service will soon support both natively, so that a single CryptoTransfer can perform atomic swaps with any arbitrary combination of fungible, non-fungible, and ℏ transfers.
We are very grateful to the Hedera user community for these interesting and powerful new feature sets.
Contributors
We'd like to thank all the contributors who worked on this release!