You can claim for any Facebook Adverts which you may have purchased (or for any ‘boosted’ posts), providing these are for the purposes of your business.
If so, they can be claimed as ‘Advertising’ or ‘Marketing’ on your tax return. Simply download the report / receipt from your Facebook account to ensure that you have records of the amounts spent on this type of marketing.
USD > GBP
Most Facebook advertisements on the platform are charged in USD (United States Dollars) and therefore can be quite tricky to add into your documentation for your business when calculating expenses.
You must use the official HMRC Exchange Rates when calculating the cost of your expenses, as these are the official exchange rates which HMRC will allow. These are usually broken down by month, and can be viewed online.
Example
Claire spends $10 on Facebook advertising in January 2018, and is invoiced in January 2018 for $10 from Facebook.
The HMRC Exchange Rate for January 2018 is $1.3406 USD = £1.00 GBP
Therefore, $10 would be £7.46.