Hmmm, you may have some digging to do.  If this is an existing client, I would be really concerned about him/her not being compliant with international returns as the exposure for not only tax liabilities but also P&I is substantial.  Failure to file certain international information returns would also toll SoL.

Notwithstanding any prior year tax treatments and issues (such as transition tax), for 2022, you will be looking at GILTI inclusion under §951A, which is taxable as ordinary income at marginal rate, and assessing whether it would be beneficial to make a §962 election to avail your client for §250 deduction and corporate tax rate (deemed FTC as well as High-Tax Exception would, presumably, not be relevant since you mentioned the business is in Berlize).  You will then also need to track E&P, PTEP, and PTI, which would have downstream implications, including on the taxation of distributions and cost basis.

At the very least, you will be preparing F.8992 to compute GILTI.  If §962 election is to be made, then, also F.8993 and F.1118.

This is very big, complex, and evolving topic.  It sounds like you don't have any experience in this area and will need to read up quite a bit.  In case you don't feel confident that you have a good handle on the technical issues and various forms, you may like to refer this client to an international tax specialist instead.

Hope this helps.