There are essentially three different types of dismissal which can occur under the Act. The first is a fair dismissal where if the specific grounds under section 6(1)  of the Act are met and the procedure under which the employee was dismissed was fair then the dismissal will be fair under the Act. It is essential for employers to have fair procedures as this can turn what would be a fair dismissal on justifiable grounds into an unfair dismissal under the Act. The second is an automatically unfair dismissal under the grounds provided for in section 6(2)  of the Act, these relate to the protected grounds such as trade union membership or pregnancy for example. Under both these types of dismissal the burden of proof in the case is important to note. In these two types of cases the dismissal is regarded by the Rights Commissioner or Tribunal as unfair. It is up to the employer then to prove (on the balance of probabilities) that the dismissal was fair. From a practical point of view then an unfair dismissal case means that the employer must show that every step along the way to dismissal was fair. This is a more hefty burden and requires showing evidence of the reason behind the dismissal and the procedures used.
The third type of dismissal under the Act is a constructive dismissal. This is a subset of unfair dismissal but the way in which it occurs is very different to the first two types of dismissal. Here the employee terminates her contract in circumstances where the conduct of the employer leaves the employee feeling they have no other option but to resign. However, in these cases the burden of proof is on the employee and so they are a more difficult case for an employee to bring.
Each type of dismissal is examined below.
(i) Fair Dismissal
Section 6(1)  of the Act provides that:
“Subject to the provisions of this section, the dismissal of an employee shall be deemed, for the purposes of this Act, to be an unfair dismissal unless, having regard to all the circumstances, there were substantial grounds justifying the dismissal.”
Section 6(4)  provides four specific grounds, which if an employer can prove that the dismissal resulted mainly from it will be deemed a fair dismissal:
A. the capability, competence or qualification of the employee,
The incapability of carrying out the worked employed to do must be inherent in the employee and cannot arise through the fault of the employee such as medical illness. 
Competence relates to the employee’s ability to do the work satisfactorily – so continual under performance with no signs of improvement can be a justifiable dismissal. The method of evaluating performance then will be crucial to whether the dismissal is, in fact, fair.
If the dismissal is based on qualification the employee must be lacking the necessary qualification to do the work he was employed to do. If the nature of the work changes making it necessary for the employee to undergo further training then they must be given a reasonable amount to time to obtain the further qualification.
B. the employee’s conduct
Conduct will usually refer to something which has affected the relationship of trust and confidence between employee and employer.  The court or tribunal will look particularly at the conduct and whether fair procedures were used during the investigation and that the employer’s actions were in all the circumstances reasonable.
C. redundancy of the employee
If it is a real redundancy as opposed to a “sham” redundancy then under the Act the dismissal will be fair. Even if the redundancy is real but the selection procedures were unfair then it cannot be a fair dismissal.
D. the employee’s continued employment would be in contravention of statute
A dismissal may be justified where continued employment might contravene a statute; for example a driver losing their driving licence or an employee’s work permit expiring or being revoked. 
In assessing whether or not a dismissal which an employer claims was under one of these grounds, the Court (or Tribunal) will look at both to establish whether the ground on which the decision was based was fair – substantive fairness – and whether the manner in which the decision was made was fair – procedural fairness. Even if the substantive ground is considered fair, if the employee was denied procedural fairness the dismissal will be considered unfair. 
The two-pronged approach to any claim of unfair dismissal can be seen in Miskella v. Keahal Limited T/A Tir nOg Creche and Montessori School.  
In Kelleher v. An Post   both the reasons for the dismissal and the procedures involved were examined by the Court. However in this case the procedures were in fact found to be “scrupulously fair”.
The decision in Kelleher v. An Post provides guidance on what will be considered to be fair procedures for example the opportunity to give responses to any accusations, an oral hearing and an appeal process.
(ii) “Automatically” unfair dismissal
Section 6(2)  of the 1977 Act provides for nine grounds upon which if a dismissal is based, either wholly or mainly then it will be deemed to be unfair:
(i) trade union membership or activities,
(ii) civil or criminal proceedings against the employer,
(iii) religious or political beliefs of the employee,
(iv) race, colour or sexual orientation of the employee,
(v) employee’s pregnancy and pregnancy-related issues,
(vi) exercise of other statutory rights, (such for example as Parental leave or Carer’s leave)
(vii) age of the employee,
(viii) membership of the Travelling Community, or
(ix) unfair selection for redundancy.
Under section 5 of the Act  in examining these types of claims a Tribunal or Court can have regard to the “reasonableness” of the conduct of the employer in relation to the dismissal.
(iii) Constructive Dismissal
The word constructive dismissal does not appear in the legislation itself but refers to dismissal in s.1(b) of the Act where it states:
(b) the termination by the employee of his contract of employment with his employer, whether prior notice of the termination was or was not given to the employer, in circumstances in which, because of the conduct of the employer, the employee was or would have been entitled, or it was or would have been reasonable for the employee, to terminate the contract of employment without giving prior notice of the termination to the employer,..
A finding of constructive dismissal means that an employee has met the threshold under the Act for an unfair dismissal, it is a type of unfair dismissal based on the breach of contract by/or unreasonable behaviour of the employer. Either the employer is guilty of conduct which amounts to a breach of contract going to the fundamental root of the contract or their behaviour to the employee is such that the employee cannot be fairly expected to put up with it. For example an employee is not actually dismissed but their working life and position is made unbearable to the extent that they are forced to resign. In these type of cases the employee must prove that but for the employer’s behaviour they would not have resigned and that in fact they were dismissed. This is slightly different to the last two categories where the burden falls on the employer to prove the dismissal was fair. It therefore is a somewhat more difficult case to take for an employee.
In the recent case of Calderon & Ors v. Nasser Rashed Lootah and Metad Alghubaisi UD1219/2013, UD1220/2013, UD1221/2013 the EAT defined the test to be met in these types of cases. (The case also deals with the concept of diplomatic immunity.) Although this case involved extreme facts it gives an up-to-date guidance on the test to be met and therefore is of value.
With regard to the burden of proof in constructive dismissal cases, the EAT held that :
“The burden of proof, which is a very high one, lies on the appellants. They must show that their resignation was not voluntary. The legal test to be applied is “an and or test”. Firstly, the Tribunal must look at the contract of employment and establish whether or not there has been a significant breach going to the root of the contract. If the Tribunal is not satisfied that there has been a significant breach of the contract it can examine the conduct of both the employee and the employer together with all the circumstances surrounding the termination to establish whether or not the decision of the employee to termination of the contract was a reasonable one.”
In this case the EAT determined that there was complete non-adherence to any of the appellants employment rights. Each and every breach in the circumstances of this case went to the root of the contract.
In the normal course of events resignation cannot be the first step taken by the employee, all reasonable options and/or procedures must be explored before an employee resigns. There is an onus on the employee to engage with the employer as can be seen in McDonnell v. Dublin Airport Authority plc.
Thus just as employers must adhere to the principles of natural justice and thus go through disciplinary procedures before a fair dismissal can be made employees too must invoke the procedures in place before resigning and claiming a constructive dismissal.
  See Reardon v. St. Vincent’s Hospital UD74/1979
  For a discussion of various types of conduct that may justify a dismissal see Cox, Corbett and Ryan (2009) “Employment Law in Ireland” Clarus Press, pp.742-750.
  The issue of work permits has been decided in recent cases, with the application for or renewal of the employee’s work permit at least an implied term of the contract – Dubyna v. Hourican Hygiene Services t/a Master Clean Services UD 781/2004 and a similar decision was reached in the case of Golovan -v- Porturlin Shellfish Ltd UD 428/2006.
  In addition to substantive and procedural fairness in an unfair dismissal an employer also owes his employees duties under the Health and Safety legislation and failure to implement these and comply with the legislation can also result in a finding of unfair dismissal. In Stobart (Ireland) Driver Services Limited v. Keith Carroll  IEHC 581 (High Court, Kearns P, 20 December 2013) the driver of a truck was terminated by the haulage company after he had made a complaint of being tired and unable to fulfil his driving duties under the Health and Safety Acts 2005 . The company argued that Mr. Carroll’s withdrawal of labour was a refusal of a reasonable request (a common law duty of an employee to his employer) and that this amounted to gross misconduct. Mr. Carroll argued that his dismissal was a penalization for making the complaint and that under the Health and Safety Acts 2005 this was an unfair dismissal. The High Court agreed and found that any penalization by an employer for a complaint by an employee under the Health and Safety Acts 2005 could amount to an unfair dismissal.