The scenario starts with a trigger that the mileage is submitted, and you post to the books some sort of expense, and mileage reimbursement payable.
How could you build a single automation to support multiple clients/submitters?
If your trigger is an Airtable form submission, you could use hidden prefilled fields
to share the same form with a number of different clients/users. Then create branching paths in your automation to post to the correct accounting file, based on who submitted it.
It isn’t perfect, someone could theoretically change with client ID in the URL, but… that would be a weird thing to do. I’d use a branded link shortener for each client’s link as well. There may be a better interface than a web form for this also. Like a mobile app.