Is there a way to create a payments page for an online product which then takes payment and passes an API instruction to my platform?

Yes, there's a way to create a payments page for the online version of the QuickBooks product, @leon10. 

We have a separate and dedicated forum that handles concerns about creating a payments page/application platform and API instructions. You'll have to visit the Intuit Developers page. This is the place where developers, like you, engage with others to discuss programming concerns. I'd recommend posting your question from there. This way, our developers can provide you ways and tips about integrating payments applications to QuickBooks. I'll guide you how. 

1. Go to this link: https://help.developer.intuit.com/s/.
2. Choose QuickBooks Online under What do you need help with?. 
3. Click Ask a Question. 
4. Log into your existing Intuit Developer Account or create a new one. 
5. Enter your concern (i.e. Create a payments page for an online product).
6. Click Ask. 

I've attached screenshots below that show the first four steps.

Additionally, I'd recommend utilizing the API articles and topics on the said page. This way, you'll be able to get helpful insights in starting to create your payments page. Just go to the API Docs & Tools menu, select QuickBooks Online, then choose either API Reference or API Explorer. Please see the screenshot below for your reference.

Please know that you're always welcome to comment below if you have other concerns or follow-up inquiries about managing customer payments and sales transactions in QBO. I'm just around to help. Take care.

@leon10 

Which platform do you have? Are using an app or developed one?