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# Algorand Specifications

If a [_heartbeat transaction_](https://specs.algorand.co/ledger/ledger-txn-heartbeat)’s [_group_](https://specs.algorand.co/ledger/ledger-transactions#group) is empty, and the [_fee_](https://specs.algorand.co/ledger/ledger-transactions#fee) is less than Tfee,minTfee,min, the transaction **FAILS** to execute unless:

- The [_note_](https://specs.algorand.co/ledger/ledger-transactions#note) NN is empty;

- The [_lease_](https://specs.algorand.co/ledger/ledger-transactions#lease) xx is empty;

- The [_rekey to address_](https://specs.algorand.co/ledger/ledger-transactions#rekey-to) RekeyToRekeyTo is empty;

- The [_heartbeat_address_](https://specs.algorand.co/ledger/ledger-txn-heartbeat#heartbeat-address), aa, is `Online`;

- The [_heartbeat_address_](https://specs.algorand.co/ledger/ledger-txn-heartbeat#heartbeat-address), aa, _eligibility_ flag (`ie`) is `True`;

- The [_heartbeat_address_](https://specs.algorand.co/ledger/ledger-txn-heartbeat#heartbeat-address), aa, is _at risk_ of suspension.

An account is _at risk_ of suspension if the current round (rr) is 100mod1000≤r≤200mod1000, and the [_block seed_](https://specs.algorand.co/ledger/ledger-block#seed) of the most recent round that is 0mod10000mod1000 matches aa in the first hbbitshbbits bits.

If successful, the `LastHeartbeat` of the specified heartbeat address aa is updated to the current round.