Definition of / guidance on internet portal, gateway or marketplace

Hello, In short, my employer is looking for further guidance on the terms mentioned in the topic of this threat. This is specifically mentioned here by HMRC: https://www.gov.uk/guidance/the-vat-rules-if-you-supply-digital-services-to-private-consumers#third-party. In UK VAT law we have found a mention of an "online marketplace" here: https://www.legislation.gov.uk/ukpga/1994/23/section/95A, but it only seems to be applicable to the sale of (physical?) goods, whereas our case deals with digital services. We are wondering who is responsible for UK VAT in the case of digital services (not goods) sold via a digital shopping cart solution (with invoice generation and payment services). For us, the terms "portal" and "marketplace" imply these rules are aiming at companies like Amazon/Uber/AirBnB, where many sellers are shown to a potential customer and the customer can chose from a selection. In the case of a shopping cart solution, the customer already starts on the seller's website and the shopping cart solution is provided by a third-party service provider. Essentially, instead of developing a shopping cart function and all the necessary other functions of selling digital services to end customers, the seller asks a third-party service provider to perform these functions for them, and the seller is still being shown as the seller to the customer on invoices. Is the provider of the shopping cart solution a "portal, gateway or marketplace"? Especially the word "gateway" seems undefined, which makes it hard for us to properly determine the VAT liability. Thanks in advance.

Hi 
The link you have referred to, https://www.gov.uk/guidance/the-vat-rules-if-you-supply-digital-services-to-private-consumers#third-party is the correct guidance for how and by whom VAT is accounted for when a supplier sells digital services via a platform
The key factors are as below:
The platform operator is supplying the consumer if the platform operator identified you as the seller but, sets the general terms and conditions, authorises payment or handles delivery or download of the digital service. Then the platform operator would be responsible for accounting for the VAT payment that’s charged to the consumer.
If you operate a digital platform that third-parties sell e-services through, you are liable to account for the VAT on those sales unless you meet all of the following conditions:
digital platforms and everyone else involved in the supply must identify who the supplier is in their contractual arrangements
invoices, bills or sales receipts must identify that supplier and the service supplied
digital platforms must not:
authorise the charge to the consumer
authorise the delivery
set the general terms and conditions of the sale
If you do not meet all these conditions:
You must treat the sales of third-party e-services as if they were your own.
You must declare any VAT that is due
The responsibility for accounting for any VAT moves back to the person who supplied you if you are giving intermediary services to that person
As per the guidance please use the VAT Clearance prodecure to receive more definitive help wiith this.
Find out about the Non-Statutory Clearance Service.
Thank you.