Sending a formal letter when resigning due to constructive dismissal is crucial. It is important to document your reasons for leaving and to provide evidence of the circumstances that led to you terminating the contract of employment. It serves to protect your rights to pursue legal action in the tribunal against your employer, if that is what you choose to do later on. The constructive dismissal letter will likely be used as evidence should you decide to take a case to the Employment Tribunal. Remember any claims to the tribunal need to be submitted three months minus one day from the date of this letter.