What are the consequences if one spouse abandons the other after a legitimate marriage contract that has not been officially registered in court?

If the marriage contract is concluded with its pillars fulfilled, it is valid, and its documentation in court is not a condition, although documenting it is preferable to preserve rights. If a divorce occurs before consummation and the wife is not the cause, she is entitled to half of the dowry, based on the Almighty's saying: "And if you divorce them before you have touched them and you have already specified for them an obligation, then [give them] half of what you specified – unless they forgo it or the one in whose hand is the marriage contract forgoes it." However, if the abandonment is from the wife due to the annulment of the marriage because of a defect in her, or because she chose separation due to the husband's hardship or apostasy, and similar reasons mentioned by scholars, then the dowry is forfeited if the annulment occurs before consummation, and she is not entitled to anything, because she is the one who caused the separation.