diff --git a/packages/webapp/src/__tests__/DepositOrWithdrawModal.test.ts b/packages/webapp/src/__tests__/DepositOrWithdrawModal.test.ts
index 171f82535..9de809754 100644
--- a/packages/webapp/src/__tests__/DepositOrWithdrawModal.test.ts
+++ b/packages/webapp/src/__tests__/DepositOrWithdrawModal.test.ts
@@ -6,6 +6,8 @@ import { signerAddress } from '$lib/stores/wagmi';
 import { readContract, switchChain } from '@wagmi/core';
 
 import type { ComponentProps } from 'svelte';
+import { getVaultApprovalCalldata } from '@rainlanguage/orderbook/js_api';
+import { getVaultDepositCalldata } from '@rainlanguage/orderbook/js_api';
 
 export type ModalProps = ComponentProps<DepositOrWithdrawModal>;
 
@@ -147,7 +149,7 @@ describe('DepositOrWithdrawModal', () => {
 		render(DepositOrWithdrawModal, defaultProps);
 
 		await waitFor(() => {
-			expect(screen.getByTestId('chain-error')).toHaveTextContent(
+			expect(screen.getByTestId('error-message')).toHaveTextContent(
 				'Switch to Ethereum to check your balance.'
 			);
 		});
@@ -173,4 +175,55 @@ describe('DepositOrWithdrawModal', () => {
 		const continueButton = screen.getByText('Deposit');
 		expect(continueButton).toBeDisabled();
 	});
+
+	it('shows loading state while checking calldata', async () => {
+		render(DepositOrWithdrawModal, defaultProps);
+
+		const input = screen.getByRole('textbox');
+		await fireEvent.input(input, { target: { value: '1' } });
+
+		const depositButton = screen.getByText('Deposit');
+		await fireEvent.click(depositButton);
+
+		expect(screen.getByText('Checking...')).toBeInTheDocument();
+	});
+
+	it('handles failed calldata fetch', async () => {
+		vi.mocked(getVaultDepositCalldata).mockRejectedValueOnce(new Error('Failed to fetch'));
+
+		render(DepositOrWithdrawModal, defaultProps);
+
+		const input = screen.getByRole('textbox');
+		await fireEvent.input(input, { target: { value: '1' } });
+
+		const depositButton = screen.getByText('Deposit');
+		await fireEvent.click(depositButton);
+
+		await waitFor(() => {
+			expect(screen.getByTestId('error-message')).toHaveTextContent('Failed to get calldata.');
+		});
+	});
+
+	it('handles deposit without approval when approval fails', async () => {
+		const handleTransactionSpy = vi.spyOn(transactionStore, 'handleDepositOrWithdrawTransaction');
+		vi.mocked(getVaultApprovalCalldata).mockRejectedValueOnce(new Error('Approval not needed'));
+
+		render(DepositOrWithdrawModal, defaultProps);
+
+		const input = screen.getByRole('textbox');
+		await fireEvent.input(input, { target: { value: '1' } });
+
+		const depositButton = screen.getByText('Deposit');
+		await fireEvent.click(depositButton);
+
+		expect(handleTransactionSpy).toHaveBeenCalledWith({
+			action: 'deposit',
+			chainId: 1,
+			vault: mockVault,
+			config: undefined,
+			subgraphUrl: undefined,
+			approvalCalldata: undefined,
+			transactionCalldata: { to: '0x123', data: '0x456' }
+		});
+	});
 });
diff --git a/packages/webapp/src/lib/components/DepositOrWithdrawModal.svelte b/packages/webapp/src/lib/components/DepositOrWithdrawModal.svelte
index 3066c256e..e2eb19afb 100644
--- a/packages/webapp/src/lib/components/DepositOrWithdrawModal.svelte
+++ b/packages/webapp/src/lib/components/DepositOrWithdrawModal.svelte
@@ -43,7 +43,11 @@
 	let currentStep = 1;
 	let amount: bigint = 0n;
 	let userBalance: bigint = 0n;
-	let switchChainError = '';
+	let errorMessage = '';
+	let depositCalldata: DepositCalldataResult | undefined = undefined;
+	let approvalCalldata: ApprovalCalldata | undefined = undefined;
+	let withdrawCalldata: WithdrawCalldataResult | undefined = undefined;
+	let isCheckingCalldata = false;
 
 	const messages = {
 		success: 'Transaction successful.',
@@ -60,7 +64,7 @@
 		try {
 			await switchChain($wagmiConfig, { chainId });
 		} catch {
-			return (switchChainError = `Switch to ${targetChain.name} to check your balance.`);
+			return (errorMessage = `Switch to ${targetChain.name} to check your balance.`);
 		}
 		userBalance = await readContract($wagmiConfig, {
 			abi: erc20Abi,
@@ -70,42 +74,45 @@
 		});
 	};
 
+	async function handleTransaction(
+		transactionCalldata: DepositCalldataResult | WithdrawCalldataResult,
+		approvalCalldata?: ApprovalCalldata | undefined
+	) {
+		transactionStore.handleDepositOrWithdrawTransaction({
+			config: $wagmiConfig,
+			transactionCalldata,
+			approvalCalldata,
+			action,
+			chainId,
+			vault,
+			subgraphUrl
+		});
+	}
+
 	async function handleContinue() {
-		if (action === 'deposit') {
-			let approvalCalldata: ApprovalCalldata | undefined = undefined;
-			try {
-				approvalCalldata = await getVaultApprovalCalldata(rpcUrl, vault, amount.toString());
-			} catch {
-				approvalCalldata = undefined;
+		isCheckingCalldata = true;
+		try {
+			if (action === 'deposit') {
+				try {
+					approvalCalldata = await getVaultApprovalCalldata(rpcUrl, vault, amount.toString());
+				} catch {
+					approvalCalldata = undefined;
+				}
+				depositCalldata = await getVaultDepositCalldata(vault, amount.toString());
+				if (depositCalldata) {
+					handleTransaction(depositCalldata, approvalCalldata);
+				}
+			} else if (action === 'withdraw') {
+				withdrawCalldata = await getVaultWithdrawCalldata(vault, amount.toString());
+				if (withdrawCalldata) {
+					handleTransaction(withdrawCalldata);
+				}
 			}
-			const depositCalldata: DepositCalldataResult = await getVaultDepositCalldata(
-				vault,
-				amount.toString()
-			);
-			currentStep = 2;
-			transactionStore.handleDepositOrWithdrawTransaction({
-				config: $wagmiConfig,
-				transactionCalldata: depositCalldata,
-				approvalCalldata,
-				action,
-				chainId,
-				vault,
-				subgraphUrl
-			});
-		} else if (action === 'withdraw') {
-			const withdrawCalldata: WithdrawCalldataResult = await getVaultWithdrawCalldata(
-				vault,
-				amount.toString()
-			);
 			currentStep = 2;
-			transactionStore.handleDepositOrWithdrawTransaction({
-				config: $wagmiConfig,
-				transactionCalldata: withdrawCalldata,
-				action,
-				chainId,
-				vault,
-				subgraphUrl
-			});
+		} catch {
+			errorMessage = 'Failed to get calldata.';
+		} finally {
+			isCheckingCalldata = false;
 		}
 	}
 
@@ -142,17 +149,23 @@
 							<Button
 								color="blue"
 								on:click={handleContinue}
-								disabled={amount <= 0n || amountGreaterThanBalance[actionType]}
+								disabled={amount <= 0n ||
+									amountGreaterThanBalance[actionType] ||
+									isCheckingCalldata}
 							>
-								{action === 'deposit' ? 'Deposit' : 'Withdraw'}
+								{#if isCheckingCalldata}
+									Checking...
+								{:else}
+									{action === 'deposit' ? 'Deposit' : 'Withdraw'}
+								{/if}
 							</Button>
 						</div>
 					{:else}
 						<WalletConnect {appKitModal} {connected} />
 					{/if}
 				</div>
-				{#if switchChainError}
-					<p data-testid="chain-error">{switchChainError}</p>
+				{#if errorMessage}
+					<p data-testid="error-message">{errorMessage}</p>
 				{/if}
 				{#if amountGreaterThanBalance[actionType]}
 					<p class="text-red-500" data-testid="error">Amount cannot exceed available balance.</p>