Duplicate Page Content due to Language and Currency

[Marketing_Today]

Hi Folks, hoping someone can help me out please

I have a site that I'd like to rank in France and the UK but I'm getting a stack of duplicate content errors due to English and French pages and GBP and EUR prices.

Below is an example of how the home page is duplicated:

http://www.site.com/?sl=en?sl=fr
http://www.site.com/?sl=fr?sl=fr
http://www.site.com
http://www.site.com/?currency=GBP?sl=fr
http://www.site.com/?currency=GBP?sl=en
http://www.site.com/?sl=fr?sl=en
http://www.site.com/?currency=EUR?sl=fr
http://www.site.com/?currency=EUR?sl=en
http://www.site.com/?currency=EUR
http://www.site.com/?sl=en¤cy=EUR
http://www.site.com/?sl=en¤cy=GBP
http://www.site.com/?sl=en
http://www.site.com/?currency=GBP
http://www.site.com/?sl=en?sl=en

Each page has the following code in the that updates according to the page you are on:

How do I simplify this and what's the correct approach?

[Marketing_Today]

Thank you so much Gianlucca! Lots to take away and get fixed.

[gfiorelli1]

I'm sorry to answer you with a question:

Why are you letting indexing the URLs with currencies?

I mean, the GB URL with Pounds is what you want to have indexed if you're geo-tarketing Great Britain, and not the GB page with the Euro currency.

The same in the case of the French version targeting France.

Said that, I kindly ask you to explain better what mean each URL you pasted in your question, so to able to answer and help you better.

http://www.site.com/?sl=en?sl=fr << What does represent this URL? SL is the language? If so, how can possibly exist a URL with two different language parameters?
http://www.site.com/?sl=fr?sl=fr << If SL is the language parameter, why in this URL it is repeated twice?
http://www.site.com << I suppose this is the canonical URL for your main language, or, instead, is it just the root and then the site applies a 302 redirection accordingly to geo-targeting?
http://www.site.com/?currency=GBP?sl=fr << Do you think is it necessary to let index a page targeting the French marketing but showing prices in Pounds? I do not think so, because the percentage of French users looking for price in another currency than Euro must be something like the 0.000001% of the entire population.
http://www.site.com/?currency=GBP?sl=en << If http://www.site.com/ is in English, targets GB and by default has Pounds as currency, than this URL should be canonicalized toward it.
http://www.site.com/?sl=fr?sl=en << What does represent this URL? SL is the language? If so, how can possibly exist a URL with two different language parameters?
http://www.site.com/?currency=EUR?sl=fr << I see that your site does not have a subfolder structure like /fr/ (and that would be the better way to go), so I imagine that this is the canonical URL for the France targeting home page, which correctly would present Euro as default currency. If it is so, this is the URL your should use in the hreflang annotation for the homepage.
http://www.site.com/?currency=EUR?sl=en << Again, if your English version is meant for geotargeting the GB market, this kind of URL (GB target but Euro as currency) should be not indexed IMHO.
http://www.site.com/?currency=EUR << I suspect this represent the homepage in the main language, but with the currency set up on Euro, correct? If so, it would be the same of the URL here below. In both cases, I would not let these kind of URL to be indexed
http://www.site.com/?sl=en¤cy=EUR << See what I wrote above
http://www.site.com/?sl=en¤cy=GBP << If everything I wrote is correct, this is a duplicate of http://www.site.com/. If it is so, these kinds of URLs should be canonicalized toward the first ones (and this is true also for URLs like the one here below and http://www.site.com/sl=en¤cy=GBP and http://www.site.com/?currency=GBP et al)
http://www.site.com/?sl=en<< See what I wrote above
http://www.site.com/?currency=GBP<< See what I wrote above
http://www.site.com/?sl=en?sl=en << If SL is the language parameter, why in this URL it is repeated twice?

Sincerely, from the URLs you gave as example, your site is not ranking not because of the hreflang, but because of the systematic production of duplicated pages, and that is something due to what seems a poor Information Architecture development.

Before even thinking about fixing the hreflang, fix the site.

[ClaytonJ]

It is generally not a problem if the content is for different users in different countries.

Unfortunately, there is no way to simplify this process. Ideally, it would be improved if you created unique content for the different language and/or groups. Google recommends creating unique content for different regions...What you have done however is correct technically.

Intrigued to see other answers posted...