French to English Law/Patents Finance (general) Certificate of achievemen

I am translating a contract and have come across this term in the table of contents - it also occurs in the annex, as a heading, but nowhere else, so am having difficulty understanding what it means.

I know 'taxe professionnelle' would be 'business tax', but I am not sure about the 'unique' - does it mean a single business tax (as opposed to several companies?) or a lump sum payment of the business tax?

The contract is from the Republic of Guinea.

I would really appreciate any help on this,

Many thanks!