I wrote this after seeing a conversation on the GrassRoots Football Facebook page. I think it is a bad idea, although no doubt well-meaning, to pay a child to score a goal.
The child who is getting paid £5 a goal, or whatever the monetary value, is harder to coach. Firstly with a binary payment system such as goal = cash, and no goal = no cash, you are telling the young player that goals are the only measure worthy of reward.
Football is a team game, and some of the best individual team-first performances won’t end up with a goal, and some of the worst can yield a goal. I would take the former every week.
Whenever the kid who is getting paid-per-goal gets the ball their focus will be on scoring. The focus on team play and making good decisions for the team will likely be overshadowed by the desire to score and be paid.
I actually found out recently that a boy I have been coaching on decision-making for years was being paid and the penny dropped for me – no wonder it has been so hard to get this particular player to make good decisions. A good decision to that boy is to score and to get paid, not to play well for the team.
There are broadly three main decisions a player has to make when they receive the ball in the final third. Pass, shoot or travel with the ball. Coaching when to make which decision to young players is hard enough without loading cash on the option to shoot.
In my opinion and in my experience, I would say don’t pay for goals.
Coaching Youth Football 
I’d like to ask the parents why they thought it was a good idea and what they hoped to achieve by it.
I pay my 7 year old son £5 a goal and he’s a strong CB he doesn’t just go for goals he plays to his position and is a great team player it’s just a little bit extra bonus if he scores. Not once has he just thought I’m scoring end of he listens to coach and gets on with it. If I want to pay £5 For my son I will do.
I have paid my son on goals for years. He is a Centre Forward so it’s kind of his job?!
I also pay on assists.
I am confident no coach he has ever had will have nothing but positives to say about his coachability.
I also pay my son for goals he scores ( striker). This reward has never been his focus during the game. He understands that for the opportunity for him to be in a position to score is a direct result from the teams play. He knows that the result is down to the team and not an individual. I totally disagree with the statement that it is hard to coach a person if there is a reward for scoring. I am the coach in this case and I have never had to challenge the players performance or attitude in the game. The team recognise his ability and role in the team and work collective to get the ball forward and create opportunities for the team to score.
Any money received as a result of scoring is paid by me and is spent on items he wants ( mainly football related). I feel he has grown and developed regardless of the possible rewards as he is a team player.