# revert_transfer · FT4 Rell API · Chromia Docs (concept)

> @mount("ft4.crosschain.revert_ transfer")
operation revert_ transfer(init_ transfer_ tx: gtx_ transaction, init_ tx_ op_ index: integer, last_ tx: gtx_ tra

Source: https://docs.chromia.com/pages/ft4-rell/-f-t4-library/lib.ft4.external.crosschain/revert_transfer/

OPERATION

# revert\_transfer

```signature
@mount("ft4.crosschain.revert_transfer")
operation revert_transfer(init_transfer_tx: gtx_transaction, init_tx_op_index: integer, last_tx: gtx_transaction, last_op_index: integer)
```

[Source](https://gitlab.com/chromaway/ft4-lib/-/blob/development/rell/src/lib/ft4/external/crosschain/operations.rell#lines-730)

Reverts a transfer that was initialized on this chain, after it has expired.
If a crosschain transfer is to be rolled back after expiring and the
assets are to be returned to the original sender, after the process
of walking the path backwards until the source chain, then this operation
should be called as the final step on the source chain to complete the
rollback. When this operation is called, the assets are returned back
to the original sender.

Throws `"INVALID TRANSFER"` if the transfer that is being unapplied was:

* never initialized on this chain
* already reverted on this chain

Throws `"INPUT ERROR"` if the input is malformed. This could be one of many different things:

* arguments found in `init_transfer_tx` and `last_tx` do not match
* `last_tx` has not been sent to the chain that comes after this one on the transfer hops

Throws`"UNSUPPORTED LAST OP"` if the operation found in `last_tx` at the given index is
neither of the three supported operations:

* `unapply_transfer` if the transfer was canceled or recalled, but it had more than one hop
  (i.e. it went from starting chain to target chain while going through at least another chain)
* `cancel_transfer` if the transfer was canceled before being applied on the chain that came
  after the init chain
* `recall_unclaimed_transfer` if the transfer was applied on the target chain, it was sent
  to a non-existing account, and it has expired

Throws `"TRANSFER NOT EXPIRED"` if the transfer being reverted did not expire

Throws if the `init_tx_op_index` does not point to `init_transfer` on `init_transfer_tx`

Throws if the required assets cannot be transferred. While this could throw in all cases
of misconfiguration considered possible for `init_transfer`, to revert a transfer it must
first have been applied. This means that the most probable scenario for the transfer of
funds to fail is if the sender blockchain account balance is lower than `amount`.

Other cases considered possible for `init_transfer` are still possible, although unlikely.
For example, the asset entity could have been deleted, which means that the asset is no
longer registered on this chain.

Anyone can call this operation, but it needs to include an `iccf_proof` operation that
`unapply_transfer` was performed on the previous chain.

**Parameters**

* **init\_transfer\_tx** — the transaction containing the `init_transfer` operation which corresponds to the transfer to revert
* **init\_tx\_op\_index** — the index of the `init_transfer` operation in `init_transfer_tx`
* **last\_tx** — the last transaction in this transfer flow, as sent to the previous hop. Note that "previous" in this context refers to the chain at n + 1 in the hops array in relation to this blockchain, since we are walking the hops array backwards. It must contain one of the three supported operations described above.
* **last\_op\_index** — the index of `apply_transfer` operation in `last_tx`

**See Also**

* `core.crosschain.applied_transfers` — to know more about the crosschain transfer workflow
* `core.crosschain.reverted_transfers` — to know more about transfer reversal

[View this page on docs.chromia.com](https://docs.chromia.com/pages/ft4-rell/-f-t4%20-library/lib.ft4.external.crosschain/revert_transfer.html)Generated API reference, mirrored from the live docs