Where your international employees resign, it’s important not to use standard US based employee exit letters. Very commonly these refer to a requirement not to work for any competitor companies for a period of months.
Such clauses are unenforceable in Europe but more significantly it can be argued they frustrate the existing employment contract as this can be seen as a change in terms and conditions leaving the employer exposed.
Furthermore, European employees are commonly very unwilling to sign such agreements which may then lead to unnecessary friction with their departure.
An employee exit letter on resignation should stick to the facts of the leaving date, notice period and the gross amount owed in salaries, commissions, bonus, any other contractual payments and unused vacation specifying the number of days outstanding.