If you're using the Classic builder, you can find that article here.
Would you like to let your clients choose how much they want to pay for your service? Or how much they can afford to donate to your cause?
You can build a typeform with a Payment field that allows your audience to donate/pay an amount of their choice.
See it at work and add it to your account – using this link while you are signed in to your Typeform account:
How to build it:
1. Add a Number question similar to this, asking how much someone wants to pay:
2. Go to the Logic panel, click Advanced and select Branching and calculations where you can set up your calculations like this:
3. Add your Payment question, and make sure you set the Price variable to 0 (zero).
4. Finish off with a nice Ending, and you’re ready to go.
Check out this second example form too: