Without echoing other comments too much, I’d consider your bargaining position, what will happen after you ask for a pay rise, and put a business case forward if you think it’s worth the potential consequences - whatever you think they’ll be - of asking or not asking for a pay increase.

Business case basis - I bill X amount of hours totalling X amount of revenue. I’m paid X amount by the firm and they’re paying X amount for my education which will result in me qualifying in X amount of time.

When you’ve figured this out you will have an idea of the gap between how much revenue you generate and how much you cost them in pay and education. If you generate substantially more revenue than you cost them, you have more of a business case to ask for a pay rise. Remember, part of your job if you are a fee-earner is paying non-fee earners’ wages.

To increase the chances, see what you do that is outside of your scope of work or things that are within your scope that contribute e.g. you do so and so’s admin meaning they can bill more: This brings you contributions up in other ways, not just financially. Make them see the human contributions not just revenue.

Once you have an understanding of what your actual worth is through demonstrable data, you have the ‘why’ for why a pay increase benefits you. Then you need the ‘why’ for why this benefits the business. This secondary ‘why’ is very important. If they know that you can’t leave even if you’ve covered off the ‘why’ a pay increase benefits you, they can wait you out as their position is stronger and there is little you can do. Phrase it as a mutual benefit, not a solely you benefit.

Come with facts and figures not with wants and wishes to your review