So I ring up the "help" line in order to give them my latest information. Once I have fought my way thru the security questions (Where did you go on holiday when you were three? What was the name of your late grandmothers cat? ) I begin to furnish them with my update. It goes like this "I've changed my job again. My present employer is...... I began on such and such a date. I will earn this amount per week. Then comes the killer question "How much have you earned in the last tax year?" Now bearing in mind that I usually have at least 2 jobs within a year and a couple of times on benefits in between times, my usual answer is "I'm not sure, but if you simply add this information to the information I last gave you last time, you will come up with an appropriate figure".
"But I can't. You have to tell me what you have earned this year and what you will earn next year" "But I can't - I can't guarantee how long I will be in this job, therefore I can't tell you how much I will earn next year (For this bit read "look you dipsh*t I don't have the gift of proficy!")
"Well you'll have to provide me with a figure"
"OK I earn x per hour and work x hours per week - do you have a calculator?"
"erm......?"
"well if you multiply the hours I work by my hourly rate then by the number of weeks in the year then you will come up with the relevant figure. Then if you add that to the information I've already given you over the past year you should find out what you want to know"
" But you have to tell me"
"Why?"
"Because this is a legal document"
"eh?"
"because this is a legal document"
"Ok - what information have I already given you?" "I can't tell you"
"Why"
"Because that's the system. You have to tell me"
"But I have already told you"
"I know. But you still have to tell me"
"But I can't"
"Why"
"Because when my employer filled in my P60 they only put 1 months earnings on it"
"But you have to tell us what you earned in the year"
"But you already have that information so if you simply add the new bit of information to the old but you'll have what you want" (but now I'm shaking and on the verge of tears)
"But I can't". At this point OH comes over and I run into the kitchen a gibbering wreck wishing desperately that my fairy godmother would appear with a large G&T) OH says to tax person "you already have this information, please put me onto your supervisor" Cue tinny on hold version of the Four Seasons - enough to drive any sane person potty. Five mins later no supervisor. OH hangs up.
I have a flash of inspiration I know - I'll ring the tax office and find out what I've earned this year. 25 mins on hold later the phone is answered and we are back to the security questions - strangely enough almost identical to the first lot.
"Can you please tell me what I've earned this year"
"No, not over the phone, we have to write to you"
"Ok no problem. I need it for my tax credit claim. Can you tell them, after all you are both dealing with my yearly earnings and are HM Revenue and customs"
"No we are a differnet department"
"I know that but since you are the same company and you have the information that they want can't you tell them?"
"no"
"Why"
"Because we are a different department (get this for and explanation) we take your money and they give you money"
"I know that, but..."
(Interrupts) "Do you want me to send you this information or not?" (In such a sarcastic tone that I can hear the eyes rolling)
"Yes please and can you please put me onto your supervisor....."
They say that if you put an infinate number of monkeys into a room with a typewriter each they can write shakespear. I don't think this is true - I think they have written the taxation system that defies logic!
Was it Fluffy? Have I guessed?
At least I dont have to do tax returns for OH now! 
sorry!!