# Money (/docs/concepts/money)

Amounts on Bittensor come in two kinds of currency: **TAO**, the chain token,
and **alpha**, of which every subnet has its own. They trade against each other
in per-subnet pools, so an alpha amount is meaningless without knowing which
subnet it belongs to — and 1 alpha on subnet 1 is not worth 1 alpha on
subnet 2.

## The Balance type [#the-balance-type]

`Balance` is unit-tagged: every instance carries the netuid whose currency it
denominates (netuid 0 is TAO). Arithmetic between different units raises
`UnitMismatchError` instead of silently mixing currencies.

```python
import bittensor as sub

sub.Balance.from_tao("10000000.123456789")   # exact TAO (str/Decimal for big amounts)
sub.Balance.from_alpha(2.5, netuid=42)       # subnet-42 alpha; prints with the subnet's
                                             # on-chain token symbol (α₄₂ before connect)
sub.tao(1.5); sub.alpha(2.5, 42); sub.rao(1_500_000_000)   # shorthands
```

Readback is unit-named too: `.tao` on a TAO balance, `.alpha` on an alpha
balance — and `.tao` on an alpha balance raises rather than pretending the
units are interchangeable. The base unit is **rao**: 1 TAO = 10⁹ rao.

## Amount parameters [#amount-parameters]

Intent fields are named by unit so there is no ambiguity about what a number
means: `amount_tao` is TAO, `amount_alpha` is the subnet's alpha (the origin
subnet for cross-subnet moves), `*_rao` is rao. Money fields that support it
accept the string `"all"` — the concrete amount is resolved from chain state at
build time (e.g. [`transfer`](/docs/tx/transfer),
[`remove-stake`](/docs/tx/remove-stake)).

## Valuing stake [#valuing-stake]

Alpha is never summed across subnets or silently treated as TAO. To value a
coldkey's stake in TAO, use the
[`stake-value-for-coldkey`](/docs/query/stake-value-for-coldkey) read: a spot
price mark (`alpha × price`, excluding slippage and fees), pinned to one block.
For what you would actually receive by exiting a position, simulate the swap
with [`quote-unstake`](/docs/query/quote-unstake), which includes fees and
slippage.

## Slippage [#slippage]

Staking and unstaking are swaps against a pool, so the trade itself moves the
price: your order consumes reserves as it fills, and the gap between what the
spot price promised and what you actually receive grows with the trade's size
relative to the pool's liquidity. Strictly, that self-inflicted gap is
**price impact**; **slippage** is the further movement from other
transactions landing before yours. The quotes account for the first, and the
limit variants protect against both. The `*-limit` variants
([`add-stake-limit`](/docs/tx/add-stake-limit),
[`remove-stake-limit`](/docs/tx/remove-stake-limit)) bound the execution price
and fail instead of filling badly.

To turn a tolerance into a `limit_price`: when staking, ceiling = spot × (1 +
tolerance); when unstaking, floor = spot × (1 − tolerance). At a spot price of
2.0 TAO ([`alpha-price`](/docs/query/alpha-price)), a 0.5% tolerance means
2.01 staking and 1.99 unstaking.

The same economics decide what is worth
[MEV-shielding](/docs/concepts/advanced#mev-shielded-submission).
Root-subnet (netuid 0) staking is not a pool swap — it converts 1:1 with no
swap fee and no price impact, so there is nothing for a front-runner to
extract and shielding it buys nothing. Small swaps (well under \~1 TAO) are
equally unattractive targets; the danger case is a large swap with a loose
or absent limit price.

## Swap fees [#swap-fees]

Every swap against a pool pays a fee of amount × FeeRate / 65535, where
`FeeRate` is per-subnet and governance-settable (default 33 ≈ 0.05%). It is
taken from the input side: TAO when staking, alpha when unstaking — and paid
to the block author (an alpha-side fee is converted to TAO first). Moving
stake between hotkeys within the same subnet is not a swap and pays no swap
fee; a cross-subnet move runs two swaps but is charged the fee only once. The
[`quote-stake`](/docs/query/quote-stake) /
[`quote-unstake`](/docs/query/quote-unstake) reads include it. This is
distinct from the per-extrinsic transaction fee — see
[the transaction model](/docs/concepts/transactions).

## Minimums [#minimums]

Two floors to know about:

* **Existential deposit** — 500 rao. An account whose balance drops below it
  is reaped: deactivated, with the remaining dust destroyed. Live value:
  [`existential-deposit`](/docs/query/existential-deposit).
* **Minimum stake** — staking operations below a chain-configured minimum
  (default 2,000,000 rao = 0.002 TAO, plus the swap fee on top) fail with
  `AmountTooLow`; unstakes are held to the same floor, both on the amount
  withdrawn and on any dust position left behind.

## Supply [#supply]

Every token is hard-capped at **21 million** — TAO and each subnet's alpha
alike. **Total issuance** is the chain's counter of what has been emitted and
not recycled; it is what halving thresholds are measured against
([emissions](/docs/concepts/emissions)). Circulating supply is smaller:
issuance includes tokens locked in pool reserves and staked positions.

## Recycled vs burned [#recycled-vs-burned]

Both remove tokens from circulation, but not equivalently. **Recycled**
tokens are subtracted from the chain's issuance counter, so the emission
schedule can re-issue them later — neuron registration costs are recycled
this way. **Burned** tokens stay counted in total issuance and are simply
gone forever; nothing re-emits them. The distinction matters when reasoning
about supply: recycling slows emission's approach to the cap, burning
permanently retires supply. Transaction fees are neither — they are paid to
the block author, not destroyed
([fees](/docs/concepts/transactions#fees)).