Contract showing trading

I know question reg this topic has been asked before...There is still a lot of confusion on the type of documents to be submitted for contracts showing trading while switching from PSW.....

My question is...

1> can this be a service contract from another company to my company...(for example: a telephone landline connection used in my business premises)

-from what i understand this proves that my company is actively trading (not dormant) and paying the bills

2> can this be an invoice (eg: my company purchasing interior design service to decorate my outlet)

3a>Does this have to be something to prove that someone is buying product/service from my company?
for eg: if mine is a software product company, should this be a contract that confirms someone has purchased my product.
3b> - if yes what if my company is in the process of developing a product for which the development will itself take 1 year?

Would be great if you guys can provide as much information on this as possible to help clear the confusion in this area.....

I read some articles... until now i'm not found the answer ..
but for 2nd question, logically your ex like interior design purchase can be the invoice ..

hope we get the right answer soon ..

Regards

ountes articacdt