From: "Peter Ibbotson" 
Newsgroups: uk.finance
Subject: Re: Sole Trader - Noob - Tax Minimisation
Date: Tue, 4 Oct 2005 11:26:29 +0100

Depending on what sort[1] of "joiner" you are, you may fall under the 
Construction Industry Scheme (aka CIS). You may well want to get an 
accountant that actually understands the scheme. In particular you'll need 
to get a Tax Certificate otherwise anyone who employs you needs to take some 
tax off your bills.

http://www.hmrc.gov.uk/pdfs/ir14-15cis.pdf

Read the above and see if you end knowing more than the accountant.

Peter

[1] If you are offering bespoke cabinet making then it probably doesn't 
apply, for window frames it may well do.