# Top up your SMS and voice-call balance

**SMS** and **voice call** alerts are billed per message, drawn from a prepaid credit balance on your account.
Email, Telegram, Slack, webhook and most other channels don't consume this balance.

## Check your balance

Open **Billing → Balances** to see your current SMS/voice credit and recent charges.

## Top up

1. Open **Billing → Balances**.
2. Click **Add funds**.
3. Choose an amount and complete payment (see [Payments & invoices](/account/payments/) for the payment
   methods HostTracker accepts).

Your new balance is available immediately after payment confirms.

## Low-balance alerts

HostTracker warns you by email before your balance runs out, so an SMS or voice alert never silently fails to
send because of an empty balance. If your balance reaches zero, SMS and voice sends stop until you top up
again - your monitors keep checking and other alert channels keep working normally.

See [SMS billing](/alerts/sms-billing/) for how message cost is calculated (message segments, destination,
channel).

## Limits and gotchas

- SMS balance is an **app-only** feature today - there is no public REST API or MCP endpoint to read your
  balance or top it up; check it from **Billing -> Balances**.
- Some plans include a starting free SMS credit and their own low-balance threshold - both are set by your
  plan, not something you configure yourself.
- Balance running out never pauses your monitors - only SMS/voice sending stops until you top up.

## Related

- [Payments & invoices](/account/payments/)
- [Alerts & contacts overview](/alerts/overview/)