You don't have to wait until you have finished working in your present job to be self employed, you can register anytime if you are doing work that generates income.
Indeed, if you are doing work outside your employment, you SHOULD be registered as under current legislation if you earn money, by whatever method, you should declare it on a tax return if it is not already taxed at source. This is stipulated under the Incomes and Corporations Taxes Act, and the Revenue don't even have to ask you, for you to be breaking the law!
Don't want anybody to be under any illusions that "if they don't know, it doesn't matter". I feel it is prudent to let anybody who is doing this "on the side" know what they are doing, legally.
Cautiously yours
Grumpy
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Just thought I would give so indicators of what can be claimed against your tax. This is from HMRC website
Decision Makers Guide - DMG35003 Allowable business expenses
Expenses which the decision maker should allow if the conditions in DMG35002 are met are all day-to-day expenses of a business including
- cleaning of business premises
- difference between opening and closing stock (on accounts)
- discounts allowed to customers
- employees' wages before any deductions are made, including any wages payable to the domestic partner
- employer's contributions to employees' pension scheme
- employer's (secondary) Class 1 SS contributions
- heating and lighting (but see DMG35104)
- hire or rental costs (but not any capital or purchase elements - see DMG35104)
- interest payable under a credit sale, a consumer credit agreement or a hire purchase agreement (but not the capital element of payments - see DMG35019)
- legal fees associated with the business
- payment in kind for work done for the business - the monetary value is allowable
- sundries, sometimes called miscellaneous items, which are small in relation to total allowable expenses provided that the decision maker is satisfied that no non-allowable expenses, for example for business entertainment, are included
- telephone, telex, fax etc (but see DMG35009)
- transport excluding any home-to-work costs - see also DMG35009 if a vehicle is used partly for private purposes
- VAT allowable (DMG31413).
Grumpy