Serious question

Although we're not earning much (if anything) with the radio plays, [edit]ferkster and I have been asked if we have an ABN.

Do any writers out there have one? Does it help at tax time? I know it offsets GST tax credits and so on, but should we get one now, or wait until some serious money comes in (I would imagine it's the latter, but I'd like to know if anyone else has had to apply for one.)