Additional agreement to an employment contract: 8 things you need to know

In the course of the employment relationship between the employer and the employee, it often becomes necessary to change the terms and conditions originally agreed - for example, a change of job, a change in working hours, a move to teleworking, a salary increase, etc. In such cases, a new employment contract is not concluded, but an additional agreement to the existing contract is used.

This document has the same legal value and reflects the specific amendments agreed to by the parties.

This article examines in detail the legal nature, the procedure for drafting and signing, the legal framework and best practices for concluding supplemental agreements to an employment contract.

1. What is the supplementary agreement

A supplemental agreement, also known as an annex to an employment contract, is a written instrument by which the parties to an existing employment contract amend one or more of its provisions. It does not constitute a new contract of employment but an addition to the existing contract.

Under Article 119 of the Labour Code, an employment contract may be amended only by mutual agreement of the parties expressed in writing. This means that any amendment must be documented and signed by both the employer and the employee in order to have legal effect.

2. Under what circumstances is an additional agreement used

A supplementary agreement is used in all cases where it is necessary to change the content of the employment contract. 

The most common occasions include:

• A change in the employee's job title or functional duties
• A change in work location (e.g., a move to another office or city)
• A change from full-time to part-time, or vice versa
• An increase or decrease in pay
• A change in work arrangements - e.g., a move to telecommuting
• A temporary or temporary appointmentAn appointment or transfer for health, pregnancy, or other protected reasons

It is important to note that a supplemental agreement is required not only for changes initiated by the employer, but also when the employee himself makes a proposal for amendment.

3. How the supplementary agreement is formed

To be valid, the supplemental agreement must meet the following requirements:

• It must be in writing
• It must be signed by both the employer and the employee
• It must contain clear wording of the changes to be made
• It must specify a specific effective date for the new terms and conditions

Here is a sample template for a supplemental agreement:How to form a supplemental agreement:

ADDITIONAL AGREEMENT 

No. 1

to Employment Contract No. 001/01.02.2022 

Today, 03.06.2025, in the city of Sofia, between:
Employer: [Name of employer], UIC: [number], represented by [name]
and
Employee: [Full name], EIN: [number]hereby enter into this Supplemental Agreement whereby the parties agree to the following amendments:

1. Effective June 10, 2025, Employee's job title shall be changed from "Office Assistant" to "Customer Service Specialist". 

2. The gross monthly remuneration shall be changed from BGN 1600 to BGN 1900.  

The other clauses of employment contract No 001/01.02.2022 remain unchanged. 

This Agreement shall form an integral part thereof.

(signatures of the parties)

4. Statutory framework and legal effect of a supplemental agreement

The main statutory provisions on supplementary agreements are found in:

• Art. 119 of the Labour Code - states that amendments to an employment contract shall be made only by mutual written agreement of the parties.
• Art. 120 of the Labour Code - allows unilateral change of place and nature of work by the employer, but only for a period of up to 45 working days in a calendar year and in case of production necessity.

Any changes not formalized by a signed supplementary agreement are legally invalid. Neither verbal bargaining nor unilaterally imposed changes are permissible outside the exceptions specified in the law.

5.What rights does the employee have before signing

The employee has every right to:

• Reject the proposed amendments without risk of unfair dismissal
• Request additional time for reflection or legal advice
• Suggest an alternative amendment

Once signed, the supplemental agreement is binding and the parties should abide by it. If the employee refuses to sign, the employer has no right to sanction or dismiss the employee without another legal reason.

6. Is it possible for the employer to unilaterally change

As a rule, the terms and conditions of employment cannot be changed unilaterally by the employer. 

The exception is Article 120 of the Labour Code, which allows the employer, in the event of industrial necessity, to unilaterally change the place or nature of work for no more than 45 working days per year, without a change in remuneration.

All other changes (job title, salary, working hours, etc.) require a signed supplementary agreement.

7. Document storage and archiving

Supplemental agreements are part of the employee's personnel file. According to Regulation No 4 of 2006, they should be kept for at least three years after termination of employment.

Agreements may also be signed in electronic form with a qualified electronic signature (QES), which has the same legal value as a manual signature.

8. Examples from practice

Example 1: An employee wishes to work 4 days a week for family reasons. The employer accepts and an additional agreement is signed to change the working hours.

Example 2: The company relocates its operations from Sofia to Plovdiv. The employee is offered an additional agreement with a new workplace. He has the right to refuse.

Example 3: An employee receives a promotion. An addendum is signed stating the new position and the increased salary.

Frequently Asked Questions (FAQ) 

Can I have more than one additional agreement to my contract?

- Yes. There is no limit to the number of supplemental agreements. Each one governs a specific change.

Does each agreement have to be filed with the NRA?

- No. Notification to the NRA is only required for a change in reportable circumstances: position, type and term of contract, hours of work.

What happens if I do not sign the proposed supplementary agreement?

- The employer cannot impose the changes without your consent. It is possible to terminate the employment relationship, but only if there is an objective and legal reason.

Conclusion

A supplementary agreement to an employment contract is an important and necessary instrument to legally reflect changes in working conditions. It ensures that both employer and employee agree to the new arrangements and creates legal certainty in the employment relationship.

It is recommended that each party carefully reviews the content of the agreement before signing. If in doubt or unclear, it is wise to seek professional legal advice.