Is a tax return needed for this small amount?

My mum used to be PAYE. She is now retired & jointly owns a property with my dad.

Her state pension is taxed at source.

The only other income she has is from the property, which I have worked out would be £257 tax owed in the 2011/12 tax year.

Does she need to register for SA and complete a tax return for this small amount? I have read the HMRC guidance which states you only need to do SA if your income from property is £2500 after allowable expenses (her share of the property income is £1285.32).

I can't believe that HMRC wouldn't want the £257 tax owed???! Can anyone enlighten me?

Thanks