The simplest way to do this is using the Statement Sales and Expenses feature.
When you have finished allocating your statement, select 'Add an Expense' in the 'Statement Sales and Expenses' section. Enter a reference for the reserve, select the category as 'Reserve' and enter the amount you would want to reserve e.g. if you statement was $1000.00 and you wanted to reserve 25%, you would enter $250.00 as the amount. Be sure to select the 'Allocate to Statement' option.
Once completed, you will have created an additional expense for each client, which will be the reserve percentage amount of the amount they received from the royalty statement.
This expense will appear on their next payment statement with the reference you entered.
To clear the reserve, which is typically done 6 to 12 months after it is placed, you have two options:
1. Simply delete the expense that you created. In this case your clients will see the additional revenue appear in the 'Previous Balance' section on their next statement.
2. Select 'Add a Sale' in the 'Statement Sales and Expenses' and enter in the same amount that you had previously reserved. Your clients will see a new item in their next statement that shows the reserved revenue being paid to them.