Around half a year ago, I performed a freelancing service for a client worth just a few hundred dollars. I did it as an individual and he paid me as a company, but I planned(and told him about it) on registering UK LTD and billing him as a company(he needs a proper bill/invoice for his accounting).
Now after some research, I am not sure if I can just open a new company and give him a proper bill for something he already paid 6months ago(the company wasn't formed yet). Can I? If not, what other options do I have? Can I bill him as an individual, say by giving him backdated invoice from hubstaff?