You say "I accepted an offer without negotiating", but that's not true. Every job is a negotiated relationship, as is every job interview. You negotiated—badly.

You say "I accepted an offer without negotiating", but that's not true. Every job is a negotiated relationship, as is every job interview. You negotiated—badly. Negotiating skills are a thing you can learn, though. I've personally accepted really awful job offers, but over the years I got better. 1. You should do research, _in advance_. Ask people, look at surveys (https://stackoverflow.com/jobs/salary/results?l=London%2c+United+Kingdom&ed=1&ex=1&ff=1&dr%5B0%5D=BackendDeveloper&tl%5B0%5D= https://stackoverflow.com/jobs/salary/results?l=London%2c+Un...), and so on. This is also part of negotiating. 2. Negotiation starts _before_ you get the offer, from the moment you apply to a job. How you interview is just as important as the final discussion over their offer. 3. As someone else said, being able to walk away strengthens you negotiating position, especially if you can demonstrate another offer. You don't have to be as aggressive as "if you can't match I'll walk", you can also just subtly set it up as a competition: "this other company gave me a really great offer, but I would love to work with you, maybe you can change the offer?" 4. When they give you an offer, you can also ask for more (https://codewithoutrules.com/2019/01/18/negotiate-like-6-year-old/ https://codewithoutrules.com/2019/01/18/negotiate-like-6-yea...). But that presumes you haven't already accepted it. See http://valerieaurora.org/howto_salary/ http://valerieaurora.org/howto_salary/ for a reasonable starting point. Not sure what to do _after_ you've accepted offer: you have far less negotiating strength at this point. However, research might suggest your salary is reasonable for London, in which case you can just revisit in a year.