There are at least a couple of possible situations in the circumstances. The issue is that it would be almost impossible to say with certainty which one it is and only a court can make that decision.
First of all it could be implied that the contract had ended, even if no official notice had been served by either party. If one of the parties, namely you as a sole trader, was no longer working and there had been no relations between you for these last couple of years then t could implied that the services had been terminated.
On the other hand, it is possible that the contract had continued to exist in place but it had simply changed the name of the parties to reflect the change of entity with which the company was dealing. So you could have this contract with all its terms still effective but instead of you as a sole trader, it would be substituted with the limited company you had created and replaced the sole trader with.
These are the two most likely scenarios. If you are unsure if the contract still exists or not and you wish to know with certainty that it has terminated, ten you should still exercise the formal termination clause in it, which requires 14 days notice to end it. Once that notice has been served the contract would officially come to an end at the end of that period.
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