# Register & reserve a parachain

Every parachain must reserve a unique identifier—the `ParaID`—that enables it to connect to its specific relay chain. Each relay chain manages its own set of unique identifiers for the parachains that connect to it. The identifier is referred to as a `ParaID` because the same identifier can be used to identify a slot occupied by a [parachain](https://wiki.polkadot.network/docs/learn-parachains) or to identify a slot occupied by a [parathread](https://wiki.polkadot.network/docs/learn-parathreads).

You should note that you must have an account with sufficient funds to reserve a slot on a relay chain. You can determine the number of tokens a specific relay chain requires by checking the `ParaDeposit` configuration in the `paras_registrar` pallet for that relay chain. For example, Paseo Testnet requires 5 PASEO to reserve an identifier:

```rust
parameter_types! {
	pub const ParaDeposit: Balance = 5 * DOLLARS;
	pub const DataDepositPerByte: Balance = deposit(0, 1);
}

impl paras_registrar::Config for Runtime {
	type RuntimeEvent = RuntimeEvent;
	type RuntimeOrigin = RuntimeOrigin;
	type Currency = Balances;
	type OnSwap = (Crowdloan, Slots);
	type ParaDeposit = ParaDeposit;
	type DataDepositPerByte = DataDepositPerByte;
	type WeightInfo = weights::runtime_common_paras_registrar::WeightInfo<Runtime>;
}
```


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