How to properly organize payment acceptance on the marketplace?

Question

Marketing

Good afternoon!
We are developing a marketplace for a narrow product niche (doors). We planned to make an online payment button on the pages of partner stores, i.e. after payment by the buyer, the money directly falls on the account of the store. Now we are communicating with Paymaster (Sberbank, Yandex-checkout refused, because according to their rules, each store should be on its own domain).
So, the Paymaster manager suggested a scheme according to which our marketplace will accept payments and transfer them to the store. Say, we kill 2 birds with one stone:

1. ease of connection. Stores will not need to go through the process of connecting to Paymaster separately.
   
2. The store will not need an online checkout. Many of them accept cash without a check, and customers with cards can be directed to our service. Those. our service acquires additional value in the eyes of stores.
   

There are a lot of questions here, here are some of them:

• is this legal at all?
  
• how does the tax authorities look at such a transit of money?
  
• how to catch crap on chargebacks?
  
• what docks does the store sign with the buyer, if for the buyer de jure the seller is our marketplace?
  

Answer 1

you do not need to connect each store separately to the payment system - this is inconvenient.
You connect an agreement for accepting card payments only for your organization and make an online cash desk for it.
You enter into an agency agreement with each of your stores, according to which, for example, your commission is 20% from each sale. For your organization's tax return, only your 20% commission (for example) is included in the tax base.
With each online purchase with a card, you accept payment and issue an online check by mail / SMS (then the store does not break the check). After a few days, transfer the money for the goods to the store minus your commission.
If you pay in cash upon receipt to the store, then you do not need to punch a check, this will be the responsibility of the store. Take this money into account in mutual settlements with your sellers. If you form too much debt, you issue an invoice to the store.
From chargebacks, you need to check the documents of each store when connecting and verify them.
For the first sale of each store, limit the amount for a certain period of time and delay before the first payment.
Also here is the API for data analysis of chargebacks https://www.maxmind.com/ru/minfraud-services
Here I answered in more detail about the marketplace How do marketplaces work in Russia?