I am not an expert on this, as my kids are in the very early years…
In the US, you don’t actually have to be accredited to issue a High School diploma. Very few places require an accredited High School diploma, and many public schools aren’t actually accredited. The main thing to do is to make sure you meet requirements of any institution in which the student wants to continue their education.
I live in Canada – and haven’t really been able to find out for sure whether my homeschool will be able to issue a Hisgh School diploma and be able to legally claim having a High School diploma on places like Job applications etc. Unlike the US, our High School diplomas are given out by the Province instead of the school. I have many years to do more research (and things can change.)
Now, for those that want an accredited diploma for homeschooling, there are places that you can pay to do that… but you have to watch as there are a lot of “paper mills” that will gladly give you a “junk” diploma (they don’t say that of course) for your money. One I have heard of that is supposed to be good is here http://www.narhs.org/, and they do take international students. A homeschool that has had children use this service with CM is here… http://www.milestonesacademy.com
What is required in the Philippines, or in the UK – I have no idea, and you will have to do the research yourself. There may be things you have to cover every year, or other legal requirements – there may not. I know in some states, homeschool students have to take a standardized test every year, or every few years… or might have to have their work evaluated etc. You need to find out what is required where you live (or what country you are from.)
Where I live, I have to give my Province a general plan (which I keep very general… for example – Language Arts, I say something like “Using Children’s Literature”) and I have to provide a report in January, and also in June. I also keep the information very general there as well.
I hope that helped some!