The merchant can check their balances with the endpoint GET /api/v2/General/Contracts/{id}/TransferBalance :

If everything is fine, it returns 200 OK and something like the below:

The field balances field holds the balances per currency:

• Keys: Currency as ISO 4217 three-letter code like "EUR" or "CHF"
• Values: Balance in the smallest currency unit, e. g. Euro Cents

The above example returns balances of € 125,017.00, and CHF 32,012.00 for the contract GCR_6NTD8NRNEH2J798BH9PD6CX8ZA5WO6.