Programmable escrow contracts

Every Coinbax Send transfer runs through an escrow smart contract on Base. The contract — not a policy, not a support team — is what holds the funds, enforces your hold window, and decides who can release or cancel. Here is exactly what it does, and the controls that run inside it.

The escrow contracts

Single-recipient escrow

The standard Send flow: one sender, one recipient, one escrow. Your USDC or USDT moves from your wallet into the escrow contract on Base and stays there for the hold window you chose.

— Only you (the sender) can cancel — and only while the hold window is open. Cancelling returns the full amount to your wallet.
— Only you can release early, at any time while the escrow is active.
— After the window passes, release to the recipient can be triggered by anyone — so funds never get stuck waiting on a third party.
— Fees are pinned when you sign: the contract rejects the transaction if fees exceed the quote you approved.
— Hold windows are enforced on-chain, from minutes up to 7 days.

Multi-recipient batch escrow

Pay several recipients in one transaction with one wallet signature. Each recipient gets their own escrow with the same hold window.

— The batch is atomic — either every payment enters escrow or none do.
— Each escrow in the batch is independent after creation: release or cancel per recipient.
— Per-recipient fee ceilings — every leg is protected by the same fee-pinning as a single send.

The controls inside them

Controls are checks that run at specific points in a transfer's life — before funds move, while they sit in escrow, and at release. They're configured once on Coinbax Send's transaction template and enforced on every send:

Sanctions screening

Before funds move

Both the sender and recipient addresses are screened against the OFAC, EU, and UN sanctions lists through Chainalysis on every send. If either side matches, the transaction stops before your wallet is ever asked to sign.

Amount limits

Before funds move

Minimum and maximum transaction bounds are checked up front, so an extra zero gets caught at the quote — not after the funds have moved.

Time-delay hold window

While funds are in escrow

The core protection: you choose how long the transfer stays reversible — from 5 minutes to 7 days. The window is enforced by the escrow contract itself, not by policy. During it you can cancel for a full refund or release early; after it, the funds release to your recipient.

SMS verification

At release · optional

An optional second factor on fund release: a one-time code sent by SMS must be verified before the escrow releases. Useful for high-value transfers where a wallet signature alone isn’t enough.

Recipient address confirmation

Before funds move · optional

Invite your recipient to confirm by email that a wallet address is really theirs before you pay it. It doesn’t block the send — it’s an extra check for first-time or high-value recipients.