---
title: "Special Methods"
description: "Special Methods in Intelligent Contracts define GenVM fallback and receive handlers for unmatched calls and value transfers."
source: https://docs.genlayer.com/developers/intelligent-contracts/features/special-methods
last_updated: 2026-06-11
---

# Special Methods

Special methods are the two methods allowed in each contract **definition** for handling undefined method calls and no-method value transfers: `__handle_undefined_method__` and `__receive__`. GenVM uses these methods when an unhandled message does not match any regular method.

> For how these methods fit into value transfer flows, see [Value Transfers](/developers/intelligent-contracts/features/value-transfers#receiving-value-without-a-method-call).

```python
class Contract(gl.Contract):
    @gl.public.write # .payable?
    def __handle_undefined_method__(
        self, method_name: str, args: list[typing.Any], kwargs: dict[str, typing.Any]
    ):
        """
        Method that is called for undefined method calls,
        must be either ``@gl.public.write`` or ``@gl.public.write.payable``
        """
        ...

    @gl.public.write.payable
    def __receive__(self):
        """
        Method that is called for no-method transfers,
        must be ``@gl.public.write.payable``
        """
        ...
```

Below is a diagram that shows how GenVM decides which method to pick, in case any regular method did not match:

```mermaid
graph TD
    unhandled_message>unhandled message] ---> has_value[has value?]

    has_value -->|yes| has_method_name[has method name?]

    has_method_name -->|yes| fallback_defined1[__handle_undefined_method__ is defined?]
    has_method_name -->|no| receive_defined[is __receive__ defined?]

    receive_defined -->|no| fallback_defined1[is __handle_undefined_method__ defined?]
    receive_defined -->|yes| receive{{call __receive__}}

    fallback_defined1 -->|yes| fallback_is_payable[is __handle_undefined_method__ payable?]
    fallback_defined1 -->|no| error3{{error}}

    fallback_is_payable -->|yes| fallback1{{call __handle_undefined_method__}}
    fallback_is_payable -->|no| error1{{error}}

    has_value -->|no| fallback_defined
    fallback_defined -->|yes| fallback2{{call __handle_undefined_method__}}
    fallback_defined -->|no| error2{{error}}
```