Doing the bigger role before the promotion is agreed

Taking on more responsibility can be a useful way to grow, but an informal arrangement can drift for months without a clear title, pay review, or decision date. There is a difference between trying a new task and quietly inheriting another person's whole job. How can someone discuss that difference constructively? Writing down the new responsibilities, support needed, and review date seems like a sensible start. The conversation becomes easier to assess when it is about a specific arrangement, rather than a general promise that the extra effort might eventually lead somewhere.