To claim your vouchers:

Go to the RedeemSG campaign listing page here
Select the campaign you want to claim vouchers for
Log in with Singpass
Enter your mobile number
Enter the OTP (you won’t be asked for this if your mobile number matches your Singpass records)
Receive your voucher link via SMS from gov.sg

For more information on how to claim your vouchers for a specific campaign, visit the campaign organiser’s page:

If you’re trying to claim vouchers for a campaign that is not listed here, contact the campaign organiser. You can find their details here.

Do I get any change back if the purchase (e.g. $8), is less than the amount of the vouchers I want to spend (e.g. $10)?