The type of assignment an employee is placed on shapes almost every aspect of their relocation: the visa category used, the package structure, the tax treatment approach, the compliance obligations in the host country, and the scope of settling-in support provided. Two employees moving to the same destination city can have materially different relocation experiences depending on whether their assignment is classified as short-term or long-term.

Understanding where your assignment sits, and what that means for the support you will receive and the obligations you carry, is an important early step in any international move.

For a full walk-through of what the international relocation process typically involves from the employee’s perspective, see the complete guide to international employee relocation.

Defining short-term and long-term assignments

There is no universal statutory definition of a short-term or long-term assignment. The distinction is primarily a policy and compliance construct applied by the organisation and its advisers based on the duration and nature of the work in the host country.

Short-term assignments (STAs) are typically defined as assignments of less than 12 months. Many organisations set the threshold at six months or 183 days, as this figure is significant for tax residency calculations in a number of jurisdictions. STAs are often used for project delivery, skills transfer, training, or to cover a business need in a market where a permanent headcount is not yet justified. For more on how organisations are using STAs strategically, see our guide on redefining talent retention through flexible short-term international work.

Long-term assignments (LTAs) typically run for 12 months or more. They involve the employee genuinely basing themselves in the host country for an extended period, with a more comprehensive relocation package and a fuller compliance framework applied. For a comprehensive overview of how long-term assignments are structured, see our guide on everything you need to know about long-term assignments.

Permanent transfers are a distinct category. The employee moves to the host country on local employment terms, and the assignment has no defined end date. This is not an expatriate assignment structure and carries different employment, tax, and immigration treatment.

Your assignment letter or policy document will confirm your classification. If the term of the assignment changes after it begins, the classification and associated support structure may need to be reviewed by your mobility team and tax adviser.

How the relocation package differs between STA and LTA

Tax and compliance differences between STA and LTA

The tax treatment of a short-term assignment is one of the most technically complex areas in global mobility, and it is the area where assumptions most frequently lead to compliance problems.

For STAs, the primary risk is that the employee creates an unintended tax liability in the host country without the employer being aware. In many jurisdictions, spending more than a defined number of days (commonly 183 days within a 12-month period) triggers tax residency obligations in that country. Where the employee’s home country also continues to tax their income, a double taxation situation arises that requires careful management by a tax adviser.

The 183-day threshold is widely referenced but is not universal. Different countries calculate the threshold differently, and bilateral tax treaties affect how it is applied between specific country pairs. Your tax adviser will determine what applies for your specific origin and destination combination and advise on the appropriate reporting and compliance approach.

For LTAs, the tax treatment is more comprehensively planned from the outset. A tax equalisation or tax protection arrangement is commonly put in place, ensuring the employee does not bear a greater tax burden as a result of the international assignment than they would have done if remaining in the home country. The tax adviser manages this arrangement for the duration of the assignment.

For a detailed guide on how expatriate tax compliance works across jurisdictions, see our expatriate tax compliance guide.

Immigration route differences

The visa or work permit route used for an international assignment is determined partly by the assignment duration and partly by the nature of the work to be carried out. Short-term and long-term assignments frequently use different immigration categories, even for the same destination country.

Many jurisdictions offer business visitor permissions or short-stay frameworks that allow employees to carry out specific activities in the host country without requiring a full work permit. These are typically limited to activities such as attending meetings, training, or internal business discussions, and do not extend to carrying out substantive employment duties. The immigration lawyer advises on whether a business visitor framework is appropriate or whether a work permit is required, based on the specific activities the employee will undertake.

For LTAs, a full work visa or work permit in the host country is almost always required. The employer acts as the sponsor, the immigration lawyer manages the application, and the employee provides documentation at defined stages.

For a detailed guide to what employer-sponsored visa applications involve from the employee’s perspective, see our guide on understanding your work visa as a sponsored employee.

What to confirm with your mobility team before the assignment begins

Assignment classification. Confirm in writing whether you are on an STA or LTA framework, and what the defined end date of the assignment is.

Tax adviser access. Confirm whether a tax adviser will be provided for the assignment and what their scope covers. For STAs in particular, early tax advice is important.

Day-count tracking. For STAs, confirm how the organisation tracks days spent in the host country and what the reporting process is.

Package scope. Confirm which package components apply to your assignment type and which are excluded.

Extension process. Confirm what happens if the assignment needs to be extended beyond the original term, including what reclassification from STA to LTA would involve.

How MovePlus supports assignment management across both types

MovePlus coordinates international assignments of all durations through the MOVEPLUS™ platform, with the compliance framework and package structure adapted to the assignment classification. The platform supports HR and mobility teams through our relocation service coordination in maintaining an accurate, real-time record of each assignee’s status, including visa position, day count, and key compliance dates.

Speak to the MovePlus team to understand how the MOVEPLUS™ platform is used to manage both STA and LTA populations within your programme. Get in touch to discuss how MovePlus can support your next assignment.