Policy for part-time work: how do you keep your mobility budget fair and correct?

1. How does part-time work affect the mobility budget?

Question: Is the mobility budget automatically adjusted in case of part-time work?

Bert: That’s a good question, because there is often confusion about this. Legally, there is no automatic pro rata requirement for part-time employees. The mobility budget is, in principle, linked to the reference car in your car policy — and that doesn’t necessarily change because someone works part-time.

The law only provides for a pro rata based on calendar days when someone starts or stops the mobility budget during the year; a pro rata based on employment rate is a policy choice made by the employer.

Still, many companies choose to adjust the budget in line with the employment rate. Why? Because in practice, it feels more logical and fair.

An employee working at 80% drives less, commutes less and therefore uses the mobility budget differently. If he or she were to receive the same budget as someone working full-time, that often feels skewed — especially within the same team or function group.

That’s why most policies include a clear rule, such as: “The mobility budget is granted in proportion to the employment rate at the time of entry.”

This creates clarity and equal treatment, and prevents discussions afterwards.

In concrete terms, this means:

• Anyone working part-time (e.g. 80%) receives 80% of the budget calculated on the basis of the reference car.
• Anyone joining during the year receives a budget pro rata the number of calendar days they participate.
• Employers working with function groups first determine an average budget per level and then apply a pro rata.

2. Do you have to calculate the budget pro rata?

Question: Is it mandatory to calculate the mobility budget in proportion to working time?

Bert: No, the law does not require that.

The mobility budget is legally based on the reference car in your car policy — not on working hours. So, in theory, a part-time employee can receive the same budget as a full-time colleague, as long as they have the same role and the same entitlement to a company car.

Still, many companies choose to calculate it pro rata. There are three reasons for this:

• Transparency: an employee working at 80% usually uses their car (or mobility options) less intensively.
• Fairness: colleagues within the same function group better understand how the budget is determined.
• Manageability: for part-time contracts, temporary hires or parental leave, a proportional calculation helps avoid mistakes.

In practice, this means, for example: Mobility budget = annual TCO of the reference car × employment rate × (number of calendar days in service / 365)

By stating this explicitly in your policy, you make it clear for employees and you also make tax audits easier. Social security mainly looks at consistency: that everyone within the same category is treated in the same way.

3. How do you deduct personal contributions from the TCO?

Question: What do you do with personal contributions when calculating the mobility budget?

Bert: That’s an important nuance that is often forgotten. When an employee pays a personal contribution for their company car — for example, because they choose a more expensive option than provided for in the car policy — that contribution must be deducted from the TCO.

Why? Because the mobility budget is based on what the employer actually pays for that car. The employee’s contribution reduces the total cost for the company, and that has a direct impact on the budget that is converted into mobility.

In concrete terms: Mobility budget = TCO of the reference car – employee’s personal contribution

That personal contribution can take different forms:

• a monthly deduction from net salary,
• a one-off payment,
• or a personal contribution to fuel or electricity costs (when not paid via a company card).

When calculating the TCO, you include all costs borne by the employer — and subtract the personal contributions to arrive at the correct net cost.

Important:

• The employer may not increase or decrease the mobility budget based on personal choices made by the employee after entering the scheme.
• Only contributions relating to the reference car before the conversion are taken into account.

Many companies set this out explicitly in their policy, for example: “If the employee has made a personal contribution for their company car, this contribution is deducted from the total annual cost of the reference car when calculating the mobility budget.”

This way, you avoid discussions afterwards and keep your calculation fully in line with federal rules.

4. How do you keep it fair between full-time and part-time workers?

Question: How do you ensure the mobility budget remains fairly distributed between full-time and part-time employees?

Bert: Fairness is crucial, because the mobility budget is about freedom of choice and equal treatment. The law does not say that part-time employees should receive less, but in practice, most employers want a system that feels logical for everyone.

That’s why some organisations work with function groups and clear calculation rules. Full-time and part-time employees within the same function group start from the same reference car — but the budgets are then applied proportionally according to their employment rate.

This keeps the logic consistent for everyone and avoids employees feeling disadvantaged or favoured.

Example:

• A full-time employee with a reference car of €700/month receives a mobility budget based on 100% of that TCO.
• A part-time colleague (80%) in the same function receives 80% of that budget.
• Both can use that budget to choose from the same mobility options in the Olympus app.

This system feels fair, transparent and legally correct.

It is also important to write this rule clearly into your policy and apply it consistently. That way, every employee knows what they are entitled to — and HR doesn’t need to make individual exceptions.

Ultimately, the mobility budget is about equal opportunities, not equal amounts. Someone who works more logically has more mobility needs. Someone who works part-time may travel less but must still have the same easy access to sustainable alternatives.

5. How do you document all of this in your policy?

Question: How do you translate all these rules — about part-time work, TCO and fairness — into a clear mobility budget policy?

Bert: The key lies in three words: clarity, consistency and transparency. Once you, as an employer, have decided how you calculate the TCO and how you handle part-time employees and personal contributions, you need to put everything down in writing in your policy. Not only because it is legally required, but especially because it will save you many discussions later on.

A good policy includes at least the following elements:

1. Definition of the mobility budget
2. Rules for part-time work and pro rata calculations
3. Personal contributions
4. Fairness and equal treatment
5. Indexation and review
6. Management and follow-up

Common mistakes (and how to avoid them)

Forgetting personal contributions

Companies do not always deduct the employee’s personal contribution from the TCO. As a result, the mobility budget is calculated too high. Explicitly state in your policy that personal contributions must always be deducted from the TCO.

No adjustment for part-time work

When someone starts working less, the budget sometimes remains unchanged. This creates inequality and fiscal risks. Ensure that the budget is automatically recalculated according to the employment rate.

Conclusion

A well-designed mobility budget requires more than numbers alone. By considering part-time workers, personal contributions and a clear TCO calculation, you create a policy that is both fair and future-proof.

Want to know how Olympus Mobility makes your mobility budget practically workable? Discover the Olympus Mobility platform and build a policy that truly adds up.