I have had a fiscal representative (my lawyer) for several years now, and retained the arrangement, even though it is no longer a requirement. Obviously being a representative involves some risk, and I understand that, and have always paid the fee required. However, my representative's only task is to pay my IMI each year, so this year I said I'd like to renegotiate the terms as I thought 246€ (included IVA) was a bit too pricey.
I transferred the full amount of the latest IMI charge, plus an additional sum to cover any short term costs whilst we sorted things out.
The reply I received was that the terms were not negotiable, and my only option was to visit the finance office and transfer the fiscal representation to myself. Unfortunately, I dithered a bit on that with the result that the IMI became payable for my wife and myself, and my representative paid one of the IMI amounts, and kept the rest. I now face court and interest charges, but still want to either change my fiscal rep, or not have one at all - but I don't really know how to go about it.
Can someone advise, please?
Thanks!

One way is to have a bank account where you can pay the IMI on line. That way, it avoids having to go in person and so long as you have the reference number for each bill, it's easy to pay with no need for any fiscal representation (BES have this facility for example).

As you say there is no need to have a fiscal rep any longer, the main requirement is to get the IMI payment request sent to you instead of to any previous fiscal rep so you know the value to pay. In order to do this you need to go to the Town Hall and show them proof of ID and proof of your actual residential address (a services bill with your name on it). With that you can make the necessary changes.

They will post the payment request to anywhere within or outside Portugal.

If you have online banking with a PT bank you can do it there, you can post a cheque or you can get a friend to pay at the post office or payshop on your behalf.

We went to the Financas in Loule to change ours and it was dead simple. Just a form to sign with I.D. Good luck!

Thanks for the replies, looks like a visit to the Financas is the way to go!