The Swedish doctrine of assumptions (förutsättningsläran) entitles one party to avoid the contract and get relief from consequential liabilities. The contract will be void and the considerations will be returned as if the contract has never existed. Today the doctrine of assumptions is particularly interesting to investigate in the context of recent global events of Covid-19. The outbreak of Covid-19 in January 2020 and pronouncement of Covid-19 being a pandemic by the World Health Organisation in March 2020 have affected nearly every organisation in the world. The range of Covid-19 pandemic and the governmental measures as a result of it are unprecedented in the modern history and have apparently brought fundamental changes in the global economy. As a result, many countries had to introduce lock-downs of the societies with various levela of restrictions which placed many countries’ economies on hold. Many factories were closed, and supply chain disrupted as just few consequences. Covid-19 has brought about the devasting affects not only on global economy, but also on contractual relationships. Many companies have, however, relied upon the force majeure clauses which is a local measure agreed between the parties in the contract. This thesis is analysing the doctrine of assumptions from the perspective of a state measure in Sweden. The purpose of this analysis is to contribute to the discussions on the doctrine’s meaning and relevance in the modern contract relationships and to suggest enshrining it into law. The doctrine of assumptions has its roots from the roman times but has been developed predominantly during 19th and 20thcenturies. It has been discussed vividly in the scientific circles in terms of its applicability, context and pre-requisites resulting in developing its subjective, objective and mixed branches. In Swedish courts the doctrine was applied already in 1930ties giving rise to its objective variant. Even though there have been differences in opinions regarding the context of the doctrine, the academics and the judges would generally be united in relation to its pre-requisites. Thus, it was important to establish that the assumption was significant, that it was foreseen by the other party and that it is reasonable to allocate the risk on the opposite party. Besides, the doctrine may apply in relation to both conscious and unconscious assumptions. For unconscious assupmtions the foreseeability element is obviously not applicable according to the academics. The doctrine of assumptions is, however, still an exemptional measure for the parties to use and as it has been shown in the case law analysis in this thesis the courts are not overly consistent in its application. The cases during the beginning of 19thcentury would focus more on the first two pre-requisites. The courts would investigate more into what an actual assumption was, its consequences and foreseeability. On the other hand, a risk balancing exercise would be observed more frequently in the cases in the end of the 19th century. In the 20th century the courts have been even less reluctant to uphold it as a valid ground for avoiding contract. The effects of the doctrine of assumptions are often challenged in the context of the other contract principles, such as pacta sunt servanda and the equivalence principle, which are contradictory to each other by definition. Pacta sunt servanda provides for freedom for the parties to contract on whatever agreed terms, the equivalence principle, on the other hand, restricts the freedom of contract by balancing the considerations between the parties. Both principles have a long history and its contexts have developed along with evolution of the values in the society. The principles can be seen as the measurement instruments in balancing the parties’ interests and considerations and are therefore central for the doctrine of assumptions according to this thesis. Furthermore, the doctrine of assumption is analysed from the perspective of its relation to 36§ of the Swedish Contract Act (AvtL) which is a legislated legal rule. These two legal tools are often compared and treated interchangeably. However, there are a number of differences in terms of their application and legal consequences. Thus, 36§ will apply to adjust the contract terms in the existing contract while the doctrine of assumptions applies where the party challenges the existence of the contract as such. Both require different legal assessments and will entail different legal consequences for the parties. Under 36§ application the contract terms may be adjusted either to the advantage or disadvantage to the party which claims it while under the doctrine of assumptions the contract will always be proclaimed void. These two legal tools should therefore be seen on its own. It is suggested in this thesis though that the doctrine of assumptions may inherit the best practices for legal assessment from the case law of application of 36§. The case law relating to the doctrine of assumptions provides good illustrations of the assumptions which are considered under the applicability of the doctrine of assumptions or at least raised by the parties. The assumptions under the Swedish doctrine of assumptions can be implied terms, misrepresentation, changed external circumstances or the contract purpose. This thesis compares further these assumptions to the similar problems in other jurisdictions. As a matter of example, the English law is briefly analysed for this comparison, and it is evident that there are designated legal rules in English law for each type of assumptions raised under the Swedish doctrine of assumptions. In English law, the parties would use the rules implied terms, misrepresentation or frustration. It might therefore be beneficial for the Swedish doctrine of assumptions to consider the examples from English law when legislating the doctrine of assumptions. The doctrine of assumptions is a controversial rule in Swedish law that originates from the doctrine or academic writings. It is not enshrined in any legislative act, but it is used in courts as a ground for proclaiming the contract void. It is argued in this thesis that the doctrine of assumption is mentioned in the academic writings, case law and government bill as having many meanings. The most accepted meaning is being a legal rule. However, the Swedish legal system is a civil law system where the legal rules derive only from the legislative acts and this meaning challenges therefore its existence since the doctrine of assumptions is not legislated and can therefore not be a legal rule per se. Some academics and judges also consider the doctrine of assumption being an interpretation tool to a legal rule. It is not though clear which rule it should interpret as it is shown in this thesis that 36§ is a separate legal rule with different pre-conditions and legal effects and there is no other rule in the Swedish law similar to the doctrine of assumptions. The Swedish contract law is based on the parties’ autonomy, and this applies rigorously in the disputes where the contract existence is challenged. This, however, needs to be viewed in the background of the other principles, such as the principle of equivalence. The contract parties cannot reasonably be expected to take on all risks in the world. That would be absurd and undermine any trust in contract law by the society. Some critics argue that when the contracts are drafted in the peace time they very rarely provide for war-related provisions. That means that whatever parties’ autonomy is, the contract is always concluded under certain pre-conditions even though these are not explicitly stated in the contract. Here it is therefore important to balance between normal and extraordinary risks. As demonstrated in this thesis, the doctrine of assumptions provides a good basis for regulating such situations where the contract is affected by the extraordinary circumstances such as Covid-related circumstances, but its context and applicability need to be clarified in law in order to be able to raise it as a legal ground for setting the contract aside in courts. There should be at least a possibility of obligatory re-negotiations. The thesis argues for legislating the doctrine of assumptions and provides further for some suggestions of the factors which need to be taken into account when evaluating and applying the doctrine of assumptions. Here the examples of the English legal tests as well as legal tests developed within 36§ area could be beneficial. Thus, it is suggested that evaluation should be based on the overall assessment which in its turn should include evaluation of all relevant circumstances. Besides this, the evaluation should be based on the equivalence principle, the contractual balance, risk distribution, the parties' balance of power, other relevant contractual terms, the ability to foresee changing conditions and mitigate the consequences of these and other relevant circumstances that can best help determine the fairness of a particular contractual relationship. Pacta sunt servanda eller att avtalet skall hållas är en av de grundläggande avtalsrättsliga principer som binder avtalsparter till att utföra prestationer de utlovat. Principen understödjer stabilitet i avtalsförhållandet trots att förutsättningarna till sådant förhållande ändras med tiden. Parterna står även för risken att vissa omständigheter kan förändras under avtalstiden, t.ex. kostnader som stiger utan att ge rätt till kompensation. Det är dock inte alla utomstående faktorer som parterna bör eller kan absorbera inom sin risktagandeförpliktelse. I motsats till avtalsbundenhetsprincipen ligger en annan avtalsrättslig princip i botten, dvs ekvivalensprincipen. Ekvivalensprincipen innebär att avtalsförpliktelser ska medföra likvärda utbyten av prestationer. Detta är relevant för riskfördelningen ifall oförutsedda omständigheter inträffar.[1] Covid-pandemin är ett av de senaste exemplen av oförutesedda omständigheter vilket påverkat samhället och den globala ekonomin oerhört mycket. Pandemin har fått breda konsekvenser för både individer och företag i världen. De ekonomiska konsekvenserna till följd av pandemin i världen blir påtagliga. De globala branscher som påverkas markant är exempelvis turistindustrin, transportindustrin och tillverkningen av elektriska komponenter och råvaror och livsmedelsindustrin. Medan turistindustrin återhämtar sig under nästkommande år, kommer en ökning av priser i den globala transportindustrin eller av elektriska komponenter att slå hårt mot de långvariga kommersiella avtalen. Det kan i sin tur leda till att en gång lukrativa avtal förvandlas till en total förlust, och det kan även driva ett påverkat företag till konkurs. I svensk rätt finns flera rättsliga verktyg vilka kan berättiga en påverkad part att avstå från avtalsbundenhet. Ett av dessa verktyg är förutsättningsläran. Förutsättningsläran är en doktrin som utgår från att en part kan befrias från sin avtalsförpliktelse om förhållandena vid tidpunkten för avtalets ingående visar sig vara oriktiga.[2] Pacta sunt servanda-principen bör inte binda parter tills de ekonomiskt blöder trots förändrade omständigheter och förutsättningar. Det bör finnas en viss avgränsning för löften som förlorar sin relevans vid bristande förutsättningar som uppkommer i ett senare skede. Ekvivalensprincipen bör, å andra sidan, återställa balansen i riskfördelningen när nya omständigheter inträffar. Syftet med uppsatsen är att bidra till diskussionen om förutsättningslärans tillämning och relevans under nya förhållanden och även undersöka lagstiftningsbehovet. Uppsatsen ska utreda huruvida förutsättningsläran kan utgöra ett rättsligt verktyg och berättiga den påverkade parten att avstå från, upphäva eller ändra kommersiella avtal i följd av Covid-pandemin och således ge rätt till åtminstone en omförhandling av avtalet. [1] Ramberg, Jan, Ramberg, Christina, Allmän avtalsrätt, 11 u., Norstedts Juridik, Stockholm, 2019, s. 32. [2] Ramberg Allmän avtalsrätt, s. 232 f.