Can I write off Goodwill balance?

Company incorporated in 2008 ( In response to Gordon Brown's 0% CT band con) with an agreed goodwill figure of £18,750. Balance before any amortisation for year to be finalised  (31/3/2011) is £4,570. Last year's turnover a mere £9,000. Any amortisation charge is not allowable for tax relief so needs to be added back in tax comps.

Only have two CT clients so do not relish having to purchase yet more software. Got caught out this year with HMRC's online CT600 not allowing adjustments re disallowable amortisation, would like to correct for future years if possible. Given that I believe the usual writedown period is 5 years can I write off the balance in one lump on the 31/3/11 accounts?

Also got caught out this year by the revenues apparent generosity re the £75 filing online incentive. You guessed it, no facility to write back on the free HMRC facility either. - that really is shameful!

Anyway if anyone could advise re goodwill query would be grateful.

Thanks