C, B, S and L are still to be implemented as stated in post 22

{C} works in sales direct invoice but only after page refresh

Attempts to set reference {C} gives me the error
Invalid placeholder 'C'. Placeholders allowed for this transaction type are: MM,YY,YYYY,UU,P.

Edit it also seems that the following is not fully implemented yet:-

File:includes\references.inc
63: //    'C' => 'customer',
64: //    'B' => 'branch',
65: //    'S' => 'supplier',
66: //    'L' => 'location'

So please comment those lines again and remove any used from transaction refs

There is more info in this wiki page This pages will inform you of what place holders can be used in which transaction type.

My own testing results in the following:-

{C} works in sales direct invoice but only after page refresh

{B} in sales direct invoice gives a warning 'Missing refline context data: 'branch'' and gives a 'B' in ref #
{S} & {L} in supplier invoice gives a warning ''Missing refline context data: 'supplier'/ 'location' and gives a 'S'/'L' in ref #

you need to uncomment:-

File:includes\references.inc
63: //    'C' => 'customer',
64: //    'B' => 'branch',
65: //    'S' => 'supplier',
66: //    'L' => 'location'

So that it reads as this:-

File:includes\references.inc
63:     'C' => 'customer',
64:     'B' => 'branch',
65:     'S' => 'supplier',
66:     'L' => 'location'

This is not currently implemented

So some examples:-

{YY}/{MM}-{001} exactly as it is written with curly brackets and YY & MM. example gives 19/02-001

{YY}{MM}-{001} exactly as it is written with curly brackets gives 1902-001

{YYYY}/{MM}-{UU}/{L}-{001} exactly as it is written with curly brackets gives 2019/02-07/4-001 where 07 = user number and 4 = location number

{YY}/{MM}/{UU}/{L}/{A001} exactly as it is written with curly brackets gives 19/02/07/4/A001 where 07 = user number and 4 = location number

{YYYY}/{MM}-{UU}-{001} exactly as it is written with curly brackets gives 2019/02-07-001 where 07 = user number

{YY}/{MM}/{UU}/{A001} exactly as it is written with curly brackets gives 19/02/07/A001 where 07 = user number

You can add or remove placeholders as you want... as per this this wiki page see the code block following 'Supported special fields for each transaction type: '

Experiment on your trial company

When you sell an item you have an option to sell from a location which you can select, this is the location that will used in the ref #

You can read about locations here.

In both casesyou will probably get just a number (of the location or pos), but you and your users will know what number each country is.

Please try on your training company first and report back for completeness.

Edit: I've had a quick look, it appears that pos can only be assigned to each user, which leaves just option 1.