How to Get Last Working Day of the every month

Create a process model with a Timer Start Event set to run daily. Connect it to a Script Task that checks if today equals the last working day using below expression. Add an XOR Gateway that routes to your monthly process when isLastWorkingDay is true, or to an End Event when false. 

By using this expression you can find last working day of every month.

a!localVariables(
  local!lastDay: eomonth(today(), 0),
  local!dayOfWeek: weekday(local!lastDay),
  local!lastWorkingDay: if(
    or(local!dayOfWeek = 7, local!dayOfWeek = 1), 
    if(local!dayOfWeek = 7, local!lastDay - 1, local!lastDay - 2),
    local!lastDay
  ),
  local!lastWorkingDay
)

What if the last working day e.g Monday is a holiday?

https://appian.rocks/2023/07/03/the-working-time-problem/

This might help you finding the closest working day.

You can use below expression

a!localVariables(
  /* Replace with your own holiday list or a rule that fetches them dynamically */
  local!holidays: {
    date(2025,8,15),
    date(2025,8,28) 
  },

  /* Get the last calendar day of the current month */
  local!lastDay: eomonth(today(), 0),

  /* Calculate last working day by moving backwards 1 workday from lastDay+1 */
  local!lastWorkingDay: workday(
    local!lastDay + 1, 
    -1,                
    local!holidays    
  ),

  local!lastWorkingDay
)

You can use below expression

a!localVariables(
  /* Replace with your own holiday list or a rule that fetches them dynamically */
  local!holidays: {
    date(2025,8,15),
    date(2025,8,28) 
  },

  /* Get the last calendar day of the current month */
  local!lastDay: eomonth(today(), 0),

  /* Calculate last working day by moving backwards 1 workday from lastDay+1 */
  local!lastWorkingDay: workday(
    local!lastDay + 1, 
    -1,                
    local!holidays    
  ),

  local!lastWorkingDay
)