Denver Research

They all mostly have the same functions.  But the cashier interfaces are different.  I think you would want either the General Retail or the Restaurant version.  These versions are easy to use with services and products without a barcode.

A charge can now be added to a sale to offset the credit card service charge.  The charge may be taxed (optional).  This update is for version 14.  Send support an email to see if you are eligible.  Older versions may require an update and small charge.  Here is how to set it up after you get the update:
 
1 – create a Fee% product.  Put the %amount (10) in the Price field. Here are the suggested settings in red:
(see pic1 attached)

2 – change Charge to Service Charge (or something).
(see pic2 attached)

3 - Settings / Payment Methods, select the Service Fee% product.

Looking for a procedure, I guess.
So - allocate payments
Run Customers with a Balance list
Tidy up any that should not have outstanding balances.
Problem here is that multiple people may put payments in, but may not allocate correctly - or - payments not put in, but someone remembers receiving it.
Thanks for your patience, ronaldrwl :-)

I am urgently seeking any business using this system, that would be willing to show me how you run your Customer accounts/monthly statements process.
Where I am working, the system has been in use for a couple of years, but the Account Receivable process has not really been addressed.
I hope this makes sense.
Thank you for your time.

No.  Each version has its own interface, terminologies and specific functions.