Onchain Recurring Subscriptions with Proration on Base: Setup for SaaS Developers

Start with Base Learn's smart contract guide, deploy in minutes. Fork SubscribeOnChain's repo, tweak for your SaaS. Install OnchainKit for frontend magic; Tina's 15-min workshop shows how.

1. Fund your Base wallet with ETH for gas.
2. Deploy subscription factory contract via Remix or Foundry.
3. Users approve Spend Permission: permit(appAddress, amount, duration).
4. Hook webhooks for offchain UI updates.

Tailor proration params: cycle length, grace periods. Test on Base Sepolia. For full flows, check this Base-specific guide. Next, we'll code the core contract, stay tuned.

Pro tip: Stablecoin integration (USDC on Base) dodges volatility, mirroring Polygon-Stripe hybrids but fully decentralized. Your decentralized SaaS recurring revenue just leveled up.

Let's roll up our sleeves and code the heart of your Base chain subscription billing system: the proration engine. Using Solidity on Base, we'll leverage timestamps for cycle tracking and atomic swaps for instant adjustments. This isn't just code; it's your revenue shield against billing disputes.

Crafting the Solidity Proration Contract

SubscribeOnChain's contracts are battle-ready, but customizing for your SaaS means overriding the prorate function. Pull from their open-source repo, deploy on Base for pennies in gas. Here's the key logic: track subscription start, compute elapsed fraction, adjust credits/debits on upgrade/downgrade. Users' Spend Permissions auto-execute pulls, no signatures needed mid-cycle.

```solidity
function upgradeOrDowngradePlan(address user, uint256 newPlanId) external {
    Subscription storage sub = userSubscriptions[user];
    require(sub.startTimestamp != 0, "No active subscription");
    uint256 currentTime = block.timestamp;
    require(currentTime < sub.startTimestamp + sub.periodDuration, "Subscription expired");

    uint256 timeElapsed = currentTime - sub.startTimestamp;
    uint256 timeRemaining = sub.periodDuration - timeElapsed;

    Plan memory oldPlan = plans[sub.planId];
    uint256 oldPricePerSecond = oldPlan.pricePerMonth / MONTH;
    uint256 unusedAmount = timeRemaining * oldPricePerSecond;

    // Refund the unused portion of the old plan
    if (unusedAmount > 0) {
        USDC.transfer(user, unusedAmount);
    }

    // Charge full price for the new plan
    Plan memory newPlan = plans[newPlanId];
    uint256 newAmount = newPlan.pricePerMonth;
    USDC.transferFrom(user, address(this), newAmount);

    // Update subscription
    sub.planId = newPlanId;
    sub.startTimestamp = currentTime;
}
```

**Note:** This function assumes the following structs and constants defined earlier in the contract:

```solidity
IERC20 public immutable USDC;

struct Plan {
    uint256 pricePerMonth; // in USDC (6 decimals)
}

struct Subscription {
    uint256 planId;
    uint256 startTimestamp;
    uint256 periodDuration;
}

mapping(uint256 => Plan) public plans;
mapping(address => Subscription) public userSubscriptions;

uint256 constant MONTH = 30 days;
```

Deploy via Foundry: forge create --rpc-url base_rpc ProrationSub --constructor-args your_params. Verify on Basescan for transparency, then integrate webhooks to notify your dashboard of pulls.

For visual clarity, check this breakdown of common proration scenarios:

Real-World Integration: Frontend and Backend Flow

Frontend? OnchainKit shines here. Tina's workshop nails a SaaS dashboard in 15 minutes: connect wallet, display active sub, trigger upgrades with one-click proration. Use Viem for tx simulation, preview adjustments before confirm. Backend: Node. js cron jobs monitor cycles, invoke contract for renewals.

1. Wrap contract ABI in OnchainKit hooks: useWriteContract({address: subFactory}).
2. Render plans table with current proration preview.
3. Handle approvals: user. grantSpend(app, USDC_amount, expiry).
4. Offchain indexer (The Graph on Base) for queryable sub history.

This stack powers decentralized SaaS recurring revenue without servers. Testnet first: Base Sepolia mirrors mainnet, zero risk. Scale to production, watch inflows stabilize via USDC.

Real talk from the trenches: I've seen forex bots falter on volatility, but Base's stablecoin subs? Rock solid. Pair with retries for failed tx (gas spikes rare on L2), and you're golden. For deeper dives, explore this implementation guide.

Testing, Launch, and Scaling Your Onchain Subs

Rigorous testing: fuzz inputs for edge cases like leap years or day-one cancels. Use Foundry tests: assert proration math pixel-perfect. Launch: announce via Farcaster, seed with early users granting permissions.

Scaling tips: Batch pulls for cohorts, optimize storage with events-only history. Monitor via Tenderly for tx traces. Revenue? Predictable, transparent, global. Users verify onchain, churn drops as trust soars.

Base's ecosystem, from ETHGlobal workshops to Base Learn, equips you fully. Fork, deploy, profit. Your SaaS just went unstoppable.