Here's a step-by-step guide on how to make tax payment on the Income Tax Portal without logging in:

Step 1: Go to the Income Tax Portal and Navigate to the 'e-Pay Taxes' Section

1. Visit the Income Tax Portal at https://www.incometax.gov.in/
2. On the left side of the home page, there is a 'Quick Links' section, click on the 'e-Pay Tax' option. You can also search for 'e-Pay Tax' in the search bar.

Step 2: Enter PAN/TAN and Mobile Number

1. On the ‘e-Pay Tax’ page, input your PAN and re-enter to confirm it. Then, provide your mobile number and click ‘Continue’.

2. Enter the 6-digit OTP received on your mobile number and 'Continue'.
    

Step 3: Select the correct Assessment Year and Payment Type

1. Select the first box labelled as ‘Income Tax’ and click on ‘Proceed’
    

1. From the ‘Assessment Year’ dropdown menu, select 2023-24
2. Under the ‘Type of Payment’, select ‘Self-Assessment Tax (300)’ and click on 'Continue'.

Step 4: Enter Tax Payment Details

Make sure to input the payment amounts correctly under the appropriate category. You may refer to the pre-filled challan on ClearTax to obtain all the necessary amounts.

Step 5: Select the Payment Method

1. Select the payment method and the bank to make the tax payment and press 'Continue'.
2. Payment can be made using internet banking, debit card, credit card, RTGS/NEFT, UPI or you can choose to pay at the bank counter.

Step 6: Verify Payment Information

1. After you click on 'Continue', there will be an option to preview the challan details.
2. Double-check the payment information you entered to ensure it is accurate, then click on the 'Pay Now' option at the bottom of the page to make the payment.
3. If you need to modify the details, click on 'Edit'.
    

Step 7: Submit the Payment

1. Tick the checkbox to agree to the Terms and Conditions after reading them and click on 'Submit To Bank'.

Step 8: Receive Payment Confirmation

You will receive a confirmation once your tax payment has been successfully submitted.

Note: Remember to download the challan as you will need the BSR code and Challan number for completing the return filing process.

Step 9: Add details on ClearTax

1. Now, resume your tax filing on ClearTax. Click on ‘Add Paid Tax Details’. 
    

1. Enter the Tax amount paid along with other details from the challan like date of payment, BSR Code, Challan Serial No.
    

You can now proceed to ‘e-file’ and ‘e-verify’ your return.