I'm a computer science Master student who is currently writing his thesis. I'm quite far in the process, most of the writing has been completed and initially I had to do some small parts before it is finished.
I received a full time job offer from a company and I've verbally accepted the offer last Friday, since I thought that I could finish my thesis at the end of this month. However, some unexpected complications took place with my research which means that I can no longer finish my thesis this month (To make it clear, I haven't signed on anything yet.)
I've asked the company before I took the offer if it was possible to start a month later, which sadly isn't the case. However, they give the option to work four days and then I could spend one day on my thesis. Although this sounds interesting, I think that one day a week would not be enough to finish my thesis. I'm afraid that it then would take way longer to finish my thesis than expected. Therefore, I've come to the conclusion to refuse the offer.
However, I do not know how I can professionally refuse this offer, especially since I've mentioned that I would not get any complications regarding my thesis. What is the best and most polite way to do this?
Lastly, I'm aware that this is not exactly good for my career and I feel bad that I have to take the step of refusing something after verbally accepting it. But I want to do this as soon as possible, so that the company is aware of it.