Having worked for a number of years as a Leagal Secretary in Wills and Probate, I'll dust off the old work hat!
Short answer? No! They cannot force you to clear the house and they cannot charge you a “skip fee” unless you voluntarily agree to take responsibility.
You say you’ve been no contact for years. You’re not inheriting anything. That means you are not automatically responsible for the estate.
When someone dies, their estate is dealt with by the executor or executrix (named in the will) or an administrator (if no will).
It is the execs legal responsibility to clear the property and deal with belongings.
If your sister is inheriting the house, then clearing it becomes part of administering the estate. That cost comes out of the estate, not out of you personally. Never has, never will be.
They also cannot just declare “it’s your stuff so you’re liable” without evidence. If you haven’t lived there for years and haven’t stored belongings there, not recipts to show that ypu purchased, that argument doesn’t stand. Even if something were yours, they would need to give you reasonable notice and opportunity to collect it before disposing of it, they can’t just send you a bill. This type thing happen all the time.
You have three key protections
You are not an executor (from what you’ve said).
You are not inheriting.
You are under any legal obligation to volunteer labour.
If they try to invoice you, you simply don’t pay. They would have to take you to civil court and prove a contractual or legal basis for the debt, which, from what you’ve described, doesn’t exist.
Emotionally this feels manipulative. Legally, it’s noise and utter nonsense!
If you want to protect yourself, you could pre-emptively send something simple in writing something like.
“I will not be involved in administering the estate and I do not accept liability for any costs relating to the property or its contents.”
Keep it factual. No emotion. No argument.
You’re allowed to stay no contact. You’re allowed to not inherit. You’re allowed to not clear a house.
This is not your responsibility!!!
I think there is something manipulative going on here, a one last attempt at gaining control over you! Stay strong!