Self Assesment and Tax Coding

Only if you want your tax to be correctly and accurately calculated.

Indeed. Do your own tax calculations using a spreadsheet - or, if you prefer, on the back of an envelope - and compare tax due with what you have actually paid. You can then decide whether it would be in your interests to fill in a tax return.

So essentially I should always request a tax form. If they owe me money, I want it back. If I owe them money I'd better pay up or risk fines & and interest etc.

Maybe I worry too much.

Many people may be short-changed by this new IR practice. Not just top rate tax payers. However, it should be pretty obvious if you have things unaccounted for in PAYE, in which case you need to get a return.

Remember PAYE = "Pretty Accurate Yet not Exact"

That's not what I said!

You don't need a tax form to work out your tax bill. Just add up all your sources of income, deduct your allowances, and then work out the first so much at 10%, so much at 22%, rest at 40%. You'll need the same information as you would put on a form - but you don't actually need to put it on a form - just do the calculation manually, or in a spreadsheet.

If you're totally incapable of doing that, you can access the forms on-line and fill them in - but don't actually submit them unless it's in your interest to do so.

If the PAYE system charges you too little tax because you have sources of income which the tax man doesn't know about, you do have a legal duty to tell him. But, if you've given him all the information, it's not unreasonable to expect him to get your tax code right. If despite this, you end up paying too little tax, keep quiet unless the tax man explicitly requires you to fill in a tax form. He ain't likely to find out and, in the event of any subsequent problems, and you have the reasonable defence that you had assumed that the PAYE system would get it right.

Or do it online - it's pretty quick and easy if you've only employment income and standard investment income (UK interest/dividends etc).

Don't forget to make a note of all Gift Aid payments and claim for these (it's suprising the things you can get gift aid for, eg zoo entrance fees, brownies subs etc).