I feel that comprehensive support is given for personal development/training. I have been in the role since March 2022 and have only been on the phone lines for about 8 weeks but there is comprehensive guidance to follow, which is step by step, and gets most of a customers questions answered on a call. In addition to this, there has also been a team of dedicated floorwalkers who are just a Teams call away to give you advice on anything you are not sure on in the guidance.
It is because of this support I feel that I have had a lot of personal development in my first few weeks in my new role with HMRC.
I joined HMRC during the lockdown and did my training online from home. You can do all of the learning via your department's online platform. Once I completed the modules, I had the opportunity to shadow colleagues via Microsoft Teams, so working from home did not effect me. There was no pressure to start and I quickly learned on the job.
In my role I was trained by team members, I also had a few opportunities to shadow colleagues taking calls. Most of the answers to common questions can be found on the departmental intranet page. I have been quite independent in finding answers to questions. Of course, there are times when you need the help of an experienced advisor, in that case, you can use the designated Teams channel where you can post a question to an experienced technical officer. However, I believe that the best training, and the quickest way to learn is by doing the job.
The experience you will receive will vary from role to role and what expertise is needed. Most roles have an induction period, this means once you arrive you will have a few days of settling in, given passes/computers/id checks etc. Dependant on the department, you may enter into an intensive training period with a mixture of online and face to face training sessions. Some departments its more learn on the job approach; with a buddy/ support system while doing training in between. The main aspect, no matter which way the training is set up, is that you have support. You can ask for help. And they are very accommodating around everyone's needs.
I joined a decade ago and don't think it would be relevant to you now. As the above answer from Abbey, it will all depend on the role you need to be an expert in.
In my 'communications' role, there's lots of support for personal development.
There's the opportunity to study for external qualifications (related to your job role) and paid for by HMRC - I was even given some study time to attend a tutorial during my working week. You can also do some job-shadowing (within HMRC and in other Government departments)
If you're dedicated and keen, I feel there are ample opportunities to develop yourself and your career. But, I can only speak for the area I work in.

Mae’r wefan hon yn defnyddio cwcis.
Rydym yn defnyddio cwcis i bersonoli cynnwys fel argymhellion swyddi, ac i ddadansoddi ein traffig. Rydych yn cydsynio i’n cwcis os ydych yn clicio "Rwy’n Derbyn". Os byddwch yn clicio ar "Nid wyf yn derbyn", yna ni fyddwn yn defnyddio cwcis ond efallai y bydd gennych brofiad defnyddiwr dirywio. Gallwch newid eich gosodiadau trwy glicio ar y cysylltiad Gosodiadau ar frig y ddyfais
Mae’r cwcis hyn yn angenrheidiol er mwyn i’r wefan weithredu ac ni ellir eu diffodd yn ein systemau. Fel arfer, dim ond mewn ymateb i gamau a wnaed gennych sy’n gyfystyr â chais am wasanaethau, megis gosod eich dewisiadau preifatrwydd, mewngofnodi neu lenwi ffurflenni. Gallwch osod eich porwr i’ch rhwystro neu eich rhybuddio am y cwcis hyn, ond ni fydd rhai rhannau o’r wefan yn gweithio wedyn.
Mae’r cwcis hyn yn ein galluogi i gyfrif ymweliadau a ffynonellau traffig fel y gallwn fesur a gwella perfformiad ein gwefan. Maen nhw’n ein helpu ni i wybod pa dudalennau sydd fwyaf a lleiaf poblogaidd a gweld sut mae ymwelwyr yn symud o gwmpas y wefan. Os na fyddwch yn caniatáu’r cwcis hyn, ni fyddwn yn gwybod pryd rydych wedi ymweld â’n gwefan, ac ni fyddwn yn gallu monitro ei berfformiad.