The total number of sick-leave days involves the assessment of the average number of working hours per week over the preceding four weeks and the total number of (partial) sick days, measured in a questionnaire. Answer categories include yes or no options and open-ended responses to express current employment status, for example date input (e.g., return to work since: ../../….).

Work performance is evaluated using scale 2A from the Maastricht Instrument for Sustainable Employability (MAISE), reflecting the long-term capacity of employees to actively engage in and contribute to the workforce. The scale consists of six statements in a questionnaire, to be completed only if work tasks have been done in the past four weeks. For example: 'I have the knowledge to perform my job well.', are measured on a 5-point Likert scale. Response categories are: 1) completely disagree, 2) disagree, 3) neutral, 4) agree, and 5) completely agree. The mean score is calculated, with higher scores indicating higher work performance.

Quality of Working Life is measured using the Quality of Working Life Questionnaire for cancer survivors (QWLQ-CS). Subscale 2 about understanding and recognition in the organization, consisting of 5 items, is included in the questionnaire. For example: 'My supervisor understands my health situation and possible complaints.', measured on a 6-point Likert scale. Response categories comprise: 1) completely disagree, 2) disagree, 3) somewhat disagree, 4) somewhat agree, 5) agree, and 6) completely agree. The sum represents the overall score, with a higher score corresponding to a higher quality of working life.

Self-efficacy pertains to the perceived capability of the employer to effectively support employees during sickness absence. This evaluation is conducted with three items concerning meaningfulness, impact and skills, of the competence scale of the Empowerment Questionnaire. For example, statements such as: 'Supporting an employee who has reported sick is a significant responsibility for me.', are measured in a questionnaire on a 6-point Likert scale. Response categories are: 1) completely disagree, 2) disagree, 3) somewhat disagree, 4) somewhat agree, 5) agree, and 6) completely agree. The mean score of the sum is calculated, with higher scores reflect higher self-efficacy.

Satisfaction with the resumption of work of the respective employee: This is measured with one self-developed question in a questionnaire: 'How satisfied are you with the work resumption process of your employee in the past month/3 months?', on a 5-point Likert scale. Response categories are: 1) very dissatisfied, 2) dissatisfied, 3) neutral, 4) satisfied, and 5) very satisfied. The category represents the overall score, with a higher score reflecting higher satisfaction.

For the process evaluation, the use of the SME tool is measured with questions regarding number of visits, duration of visits, tool availability and web analytics. For example with the question: 'How often have you visited the SME tool in the past three months?'. Response categories comprise multiple choice and open ended options.

For the process evaluation, the perceived usefulness of the SME tool is measured with self-developed questions regarding the usefulness of the tool, enhancement of knowledge and skills, and likelihood of recommending the tool to colleagues. For example through the question: 'Would you recommend the tool to other employers when guiding an employee who has reported ill?'. Response categories are multiple choice and open ended options.

For the process evaluation, the logic model of change components consists of the constructs: autonomy, competence, relatedness and ability. These are measured in self-developed questions such as: 'I have the skills to support an employee on sick leave.', measured on a 6-point Likert scale. Response categories comprise: 1) completely disagree, 2) disagree, 3) somewhat disagree, 4) somewhat agree, 5) agree, and 6) completely agree. Individual scores represent the overall score of individual component, with higher score reflecting higher autonomy, competence, relatedness and ability.

For the process evaluation, the interpretation of the results from the RCT and potential implementation strategies for the national implementation of the tool will be explored via one-time interviews with 5-10 employees, 5-10 employers, and 5-10 OPs, out of a purposive sample of RCT participants.