Hello
as I understand if you are autonomo you have to be
IVA registered But can you claim the IVA back if you are charged this on invoices that you have paid out ?
also do you charge IVA for work you carry out as per the UK and include this on your invoices ?

thank you

Say you spend more than you earn, you wont have to pay nothing but you wont get jack back in the first qtr or remaining qtr's, you have to wait til the end of the year before you can claim any excess, Its a reason I have found they love UK companies and others to buy from but when the situation is reversed they say go claim it back in your home country.

When you write about autonomo what type are you going to be?
Looking around the web you will be an intermediary in the tax collection system, just like all V.A.T. systems. This is just one example.
I would strongly advise you to get a good gestoria.
In the meantime maybe read through the following website which has useful and complicated answers to various questions.
Guía del autónomo

It depends on what service you are providing/product you are selling. And whether your customers are in Spain or in other EU countries or non-EU countries.

Good idea to get some professional advice